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Revue canadienne d’audition Vol. 5 No. 6

Comparative Review of Cardiovascular Health and Hearing

Helmholtz Resonators: They Are Everywhere!

Peer Reviewed

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lmost 30 years ago, my first job was as a vent-associated resonance to a study of room Astaff audiologist at the Canadian Hearing acoustics, and this article extends our Society. The sound booths were located in a knowledge of what we already thought we converted garage in a three story house that once knew about Helmholtz resonators. Scott’s was the Finnish embassy. I had three colleagues previous incarnation was in the automotive (Tani Nixon was my boss and mentor, Glen industry and some of the examples derive Sutherland who knew everything about aural from his tenure there. The science and even rehabilitation and knew the best restaurants in some of the technology is easily transferable Toronto, and the third was another Marshall – to the field of audiology. Marshall Rosner). If Tani came into our shared offices and said “Marshall!” we became very Phillipe Fournier has written on the adept at figuring out who was in trouble. Our perceived benefits of using FM systems with first jobs in audiology are always important. They teach you cochlear implants. Like hearing aids, cochlear implants are the “ropes” that you didn’t learn about in school. And to this limited in many situations and the use of assistive listening day, I have close friendships with all these colleagues. The devices to improve the signal to noise ratio is always useful. I Canadian Hearing Society is now celebrating their 70th am actually quite surprised by how infrequently assistive anniversary and Rex Banks (the current Tani) gives us a nice listening devices such as FM systems are being recommended overview of where they were and where they are today. by our colleagues. Phillipe is a student at the University of Ottawa and an abstract of his work appears under the banner Speaking of anniversaries, the School of Communication of “From the Classrooms.” Isabelle-Anne Pleau, also a student Sciences and Disorders at the University of Western Ontario at the University of Ottawa, has sent in an abstract as well and is celebrating their 40th anniversary. Dr. JB Orange gives an has tried to tease apart threshold information (with and excellent overview of their program and the celebrations. And without masking) in an attempt to delineate the relative does anyone know what the “JB” stands for? contributions of sensory and non-sensory contributions as a function of age. On a different topic, I always knew that doing my push ups (and sit ups and crunches, and…) was supposed to be good To round out this issue of the Canadian Hearing Report, we for me, but now we have data showing that being in good have a short piece that is written “For the Consumer” on noise cardiovascular shape actually minimizes the chances of cancelling headphones. Please note that this article can be sensori-neural hearing loss down the line. A peer-reviewed freely copied and given out to clients as desired. Noise article (Canadian Hearing Report does offer the opportunity of cancellation has been around since the 1930s but only having a submission peer reviewed) has been submitted by recently has it found its way into consumer products and Doctors Hutchinson and Alessio showing that elderly couch hearing aids. It is hoped that this is the first of many free-use potatoes actually have a greater sensori-neural hearing loss “For the Consumer” information sheets that will appear in than their age-matched physically fit colleagues. It seems that upcoming issues of Canadian Hearing Report. presbycusis is not inevitable, or at least not to the same degree. I would like to take this opportunity to wish everyone and I recently ran into Scott Lake who is an engineer with Westone their families a pleasant and peaceful holiday season. Laboratories at an American Academy of Audiology meeting and I managed to “persuade” him to write an article for us on Marshall Chasin, AuD one of my favourite topics – the acoustics of Helmholtz Editor-in-Chief resonators. We have them everywhere in audiology, from the

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on premier emploi, près de 30 ans “persuader” de nous écrire un article sur un Mmaintenant, a été à la Société de mes sujets de prédilection– l'acoustique canadienne de l'ouïe en tant qu'audilogiste. des résonateurs de Helmholtz. Nous les avons Les cabines de sons étaient situées dans un partout en audiologie, de la résonance garage converti en maison de trois étages qui associée à l'évent à l'étude de l'acoustique de abritait jadis l'ambassade de la Finlande. chambre, et cet article élargit notre savoir au J'avais trois collègues (Tani Nixon était ma sujet des résonateurs d'Helmholtz. Scott, dans patronne et ma conseillère, Glen Sutherland une autre vie, est passé par l'industrie savait tout sur la réhabilitation auditive et les automobile et certains des exemples meilleurs restaurants de Toronto, et le découlent de son passage. La science et même troisième était un autre Marshall –Marshall certaines technologies sont facilement Rosner). Si Tani venait dans le bureau qu'on transférables au domaine de l'audiologie. partageait et appelait “Marshall!”, nous savions pertinemment qui, de nous , était en difficulté. Nos premiers Phillipe Fournier a déjà écrit au sujet des avantages présumés emplois en audiologie sont toujours importants. Ils vous de l'utilisation des systèmes MF avec les implants cochléaires. enseignent les “rouages” que vous n'avez pas appris à l'école. Comme les appareils auditifs, les implants cochléaires sont Et à jour, j'ai des relations d'amitiés étroites avec tous ces limités dans plusieurs situations et l'utilisation des appareils collègues. La Société canadienne de l'ouïe célèbre maintenant fonctionnels pour malentendants pour améliorer le rapport son 70ième anniversaire et Rex Banks ( le Tani d'aujourd'hui) signal/bruit est toujours utile. En fait, je suis assez surpris nous donne une belle vue d'ensemble du passé et du présent. que nos collègues ne recommandent pas plus souvent les appareils fonctionnels pour malentendants comme les En parlant d'anniversaires, the School of Communication systèmes MF. Phillipe est étudiant à l'université d'Ottawa et Sciences and Disorders de l'université de Western Ontario un résumé de son travail apparaît sous la bannière “From the célèbre son 40ième anniversaire. Dr. JB Orange nous offre Classrooms.”. Isabelle-Anne Pleau, aussi étudiante à une excellente vue d'ensemble de leur programme et des l'université d'Ottawa, a envoyé aussi un résumé et a essayé célébrations. Et est ce quelqu'un connait la signification du de dissocier le seuil de l'information (avec ou sans masquage) “JB”? dans une tentative de délimiter les contributions relatives des contributions sensorielles et non sensorielles comme une Passant à autres chose, j'ai toujours su que faire mes tractions fonction de l'âge. sur les mains (et redressements assis et enroulements abdominaux, et... ) était sensé m'être salutaire, mais nous Pour terminer en beauté ce numéro de la Revue canadienne avons maintenant des données qui montrent qu'être en d'audition, nous avons un papier court qui est écrit “Pour le bonne forme cardiovasculaire minimise les chances de consommateur” traitant des écouteurs suppresseurs de bruit. surdité neurosensorielle en fin de compte. Un article évalué Veuillez noter que cet article peut être librement copié et par les pairs ( la Revue canadienne d'audition offre donné au clients selon son bon vouloir. La suppression de l'opportunité de recevoir des soumissions évaluées par les bruit est présente depuis les années 30, mais seulement pairs) a été soumis par Dr Hutchinson et Dr Alessio montrant dernièrement, elle a trouvé son chemin dans les produits que les personnes âgées sédentaires ont une plus grande pour consommateurs et appareils auditifs. Nous espérons surdité neurosensorielle que les personnes âgées du même que ce sera le premier de plusieurs papiers “Pour le âge mais physiquement actives. Apparemment, la consommateur” libres d'utilisation qui vont apparaître dans presbyacousie n'est pas inévitable, ou tout au moins pas au les prochains numéros de la Revue canadienne d'audition. même degré. Je voudrai saisir cette opportunité pour souhaiter à toutes et à tous ainsi que vos familles des temps de fêtes paisibles . Je suis tombé dernièrement sur Scott Lake qui est un ingénieur avec Westone Laoratories au cours d'une réunion Marshall Chasin, AuD de l'American Academy of Audiology, et j'ai réussi à le Éditeur en chef

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To learn more about how you and your clients can have it all with Moxi 3G, visit www.unitron.com/ca or call 1.800.265.8255 Vol.5 No 6, 2010 | contents Revue canadienne d’audition DEPARTMENTS ______Vol.5 No 6, 2010 3 Message from the Editor-in-Chief Message du L’editeur en chef Official publication of the Canadian Academy of Audiology ACADEMY NEWS

8 “Quick Notes” From The Executive Director “Dépêches rapides ” Du directeur exécutif Publication officielle de l’académie canadienne d’audiologie www.canadianaudiology.com AUDIOLOGY NEWS

E DITOR- IN-CHIEF /ÉDITEUR EN CHEF 11 Audiology History at The Canadian Hearing Marshall Chasin, AuD., M.Sc., Reg. CASLPO, Society: 70 Years of Excellence Director of Research, Musicians’ Clinics of Canada BY REX BANKS

A SSOCIATE E DI TORS /ÉDITEU RS ADJOINTS Ronald Choquette, MOA, AuD Campbellton Regional Hospital 13 Celebrating 40 Years of Academic Excellence Leonard Cornelisse, MSc, Unitron Hearing in Audiology and Speech-Language Pathology Joanne Deluzio, PhD, Audiologist, Reg. CASLPO, at the University of Western Ontario University of Toronto BY JB ORANGE Lendra Friesen, PhD, Sunnybrook Health Sciences Centre Bill Hodgetts, PhD, University of Alberta 38 Hearing News Network Lorienne Jenstad, PhD, University of British Columbia André Marcoux, PhD, University of Ottawa 38 Noise and Chemicals: Workers Are Calvin Staples, MSc, Conestoga College Losing Their Hearing FEATURES Rich Tyler, PhD, University of Iowa Michael Valente, PhD, Washington University 38 Reinventing the Road RESEARCH AND

M ANAGING E DITOR /DIRECT EUR DE LA R ÉDACTION DEVELOPMENT FOCUS Scott Bryant, [email protected] 2020 Examination of the Associations

C ONTRIBU TORS COLUMNS between Cardiovascular Health Helaine Alessio, Rex Banks, Marshall Chasin, and Hearing: Comparative and Philippe Fournier, Lendra Friesen, Kathleen Hutchinson, 15 FOR THE CONSUMER Historical Perspectives Scott Lake, Tom McFadden, JB Orange, Isabelle-Anne Pleau Noise Cancelling Headphones BY KATHLEEN M. HUTCHINSON AND BY MARSHALL CHASIN HELAINE M. ALESSIO A RT D IRECTOR/DESIGN /DIRE CTEUR ARTISTIQUE /DESIGN Andrea Brierley, [email protected] 16 SPOTLIGHT ON SCIENCE Helmholtz Resonators: Do ABRs Affect DPOAEs? 3131 They Are Everywhere! SALES AND CIRCULATION COORDINATOR./ COORDONATRICE DES VENTES ET DE LA DIFFUSION BY LENDRA FRIESEN BY SCOTT LAKE Brenda Robinson, [email protected]

ACCOUNT ING /COMPTAB ILITÉ 18 FROM THE CLASSROOM: University of Ottawa Susan McClung Unmasked Thresholds and Minimum Masking in Infants and Adults: A Timeline for Separating G ROUP P UBLISHER /CHEF DE LA DIRE CTION Sensory from Nonsensory Contributions to John D. Birkby, [email protected] Infant-Adult Differences in Behavioural ______Thresholds BY ISABELLE-ANNE PLEAU Indicates peer reviewed article. Canadian Hearing Report is published six times annually by Andrew John Publishing Inc. with offices at 115 King Street West, Dundas, On, Canada 19 Users’ Perspectives on the Benefits of FM L9H 1V1. Systems with Cochlear Implants We welcome editorial submissions but cannot assume responsibility or BY PHILIPPE FOURNIER commitment for unsolicited material.Any editorial material, including pho- tographs that are accepted from an unsolicited contributor, will become the property of Andrew John Publishing Inc. FEEDBACK We welcome your views and comments.Please send them to Andrew Publications Agreement Number 40025049 • ISSN 1718 1860 John Publishing Inc., 115 King Street West, Dundas, On, Canada L9H 1V1. Copyright 2010 by Andrew John Publishing Inc. All rights reserved. Return undeliverable Canadian Addresses to: Reprinting in part or in whole is forbidden without express written con- sent from the publisher. INDIVIDUAL COPIES Individual copies may be purchased for a price of $19.95 Canadian. Bulk orders may be purchased at a discounted price with a minimum order of 25 copies. Please contact Ms. Brenda Robinson at (905) 628-4309 or REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 7 brobinson@andrewjohn publishing.com for more information and specif- ic pricing. | aCadeMY neWs “QUICK NOTES” FROM THE EXECUTIVE DIRECTOR

very busy fall season for CAA began • Mary MacDonald, University of to tell us about your National Audiology Ain earnest with our 2010 British Columbia Week activities. Conference and Exhibition held • Robert Murphy, Dalhousie University October 5–8 at Le Centre Sheraton in Now that our bid to co-host with Montreal. Delegates heard from an The Canadian Inter-organizational CASLPA the International Society of outstanding line-up of international Steering Group for Audiology and Audiology Congress in Vancouver, speakers, highlighted by Dr. Richard Speech-Language Pathology recently British Columbia, in October 2016 has Gans who gave the keynote address. released proposed Competency Profiles been accepted, we will be searching for a Social highlights included a “CAA’s Got for the profession, and asked its member hotel venue, recruiting conference co- Talent Show” during the Opening organizations, including CAA, to provide chairs and members to participate on the Reception, and a Soiree Evening with feedback by November 30, 2010. In Planning Committee, and a professional live entertainment by impressionist/ addition, CAA is taking the lead role in a congress organizer to manage the event. comedian Mat Gauthier. The CAA Trade project to develop Guidelines for If you are interested or know of someone Show once again provided a wealth of the Assessment, Diagnosis and who is within CAA, contact me at information about latest trends in Intervention/Mediation of Auditory [email protected] audiology services and hearing Processing Disorders (APD). The equipment and supplies. I wish to thank guidelines should be available early in Finally, the 2nd Annual CAA Spring our sponsors, manufacturers, and 2011. Audiology Seminar will be held at the suppliers as well as all those who beautiful Delta Beausejour Hotel in attended the conference for their The Federal Healthcare Partners (FHP) Moncton, New Brunswick. After last continuing support. / Third Party Payers Group met again year’s very successful inaugural event in with representatives of CAA and CASLPA Richmond, British Columbia, we will This year’s President’s Award recipient in Montreal during the CAA Conference once again be featuring Dr. Michael was Anne Griffin, a renowned audio- to discuss items of concern to Canadian Valente, director, Division of Adult logist with the Central Health Care Board audiologists. The FHP Group includes Audiology, Washington University in Grand Falls, Newfoundland. Veterans Affairs Canada (VAC), Non- School of Medicine in St. Louis, Missouri. Insured Health Benefits (NIHB), Online registration at www.canadian The Jean Kienapple Award for Clinical Department of National Defense (DND), audiology.ca opens on December 1 and Excellence went to Sonia Marazzi, a the RCMP, and Blue Cross. A full report space will be limited respected audiologist with the North on decisions and recommendations Shore Children’s Hearing Clinic in North coming out of our meeting will be posted Vancouver, British Columbia. soon on the Third Party Payer page of our website. The recipient of the Student Poster Award for Outstanding Research was A further meeting was held with the Christine Turgeon from the University NIHB group on September 30th to of Montreal. Other Student Award discuss the many questions from CAA winners as nominated by their respective members specific to NIHB. schools were: We recently celebrated National • Emilie Gosselin, University of Audiology Week (October 18–24, Montreal 2010). The CAA marketing team produced • Bonnie Lampe, University of Western an online Media Tool Kit to assist CAA Tom McFadden Ontario members in promoting the profession. Go Executive Director • Maxime Maheu, University of Ottawa to www.canadianaudiology.ca/myNAW Canadian Academy of Audiology

8 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION Les nouVeLLes de L’aCadÉMie | “DEPECHES RAPIDES” DU DIRECTEUR EXECUTIF

Une saison d'automne bien chargée a • Mary MacDonald, University of membres de l'ACA dans leurs efforts pour commencé avec notre Conférence et British Columbia promouvoir la profession. Veillez visiter le exposition 2010 qui s'est tenue du 5 au 8 • Robert Murphy, Dalhousie University www.canadianaudiology.ca/myNAW pour Octobre au Centre Sheraton à Montréal. nous faire part de vos activités durant la Nos délégués(es) ont eu droit à des Le groupe directeur interorganisations semaine nationale de l'audiologie. conférenciers exceptionnels de renommée pour l'audiologie et l'orthophonie a internationale, le tout couronné par dernièrement publié les profiles de Maintenant que notre soumission pour Dr. Richard Gans qui a été le conférencier compétences proposés pour la profession, être le co-hôte avec l'ACOA, du Congrès d'honneur. Parmi les moments sociaux et a demandé aux organisations membres, de la Société internationale d'audiologie phares, le spectacle “CAA’s Got Talent ” y compris l'ACA, de fournir une à Vancouver, en Colombie Britannique en à la réception d'ouverture, et une rétroaction au plus tard le 30 Novembre Octobre 2016, a été acceptée, nous allons Soirée Evening avec le spectacle sur scène 2010. De plus, l'ACA joue un rôle de chef faire la recherche de l'hôtel, le recrutement de l'impressionniste/ humoriste Mat de file dans un projet qui vise à développer du président ou de la présidente et des Gauthier. Le Salon professionnel de Des lignes directrices pour l'évaluation, membres pour participer au comité de l'ACA a encore une fois fournit une le diagnostic et l'intervention/ médiation planification, et le recrutement d'un groupe richesse en informations sur les dernières des troubles des traitements des professionnel de planification de congrès tendances en services audiologiques, informations auditives. Les lignes pour gérer l'événement. Si vous êtes ou équipements et fournitures auditifs. Je directrices devraient être disponibles tôt en connaissez quelqu'un de L'ACA qui serait voudrais remercier nos commanditaires, 2011. intéressé(e), veuillez me contacter au fabricants, et fournisseurs ainsi que tous [email protected]. ceux et toutes celles qui ont participé à la Le groupe Partenaires au niveau fédéral conférence pour leur soutien continu. en matière de soins de santé/Tiers Finalement, le 2eme séminaire annuel du payants s'est encore réunit avec des printemps de l'audiologie se tiendra au La récipiendaire du Prix du président de représentants(es) de l'ACA et l'ACOA à beau hôtel Delta Beausejour à Moncton, cette année est Anne Griffin, une Montréal pendant la conférence de l'ACA, dans le Nouveau Brunswick. Suite à audiologiste de renom du Central Health pour discuter des sujets de préoccupations l'événement inaugural très réussi de l'année Care Board à Grand Falls, à Terre Neuve. des audiologistes canadiens. Parmi le dernière à Richmond, en Colombie groupe des partenaires au niveau fédéral en Britannique, nous recevrons encore Dr. Le Prix Jean Kienapple pour l'excellence matière de soins de santé, les Anciens Michael Valente, directeur, division de en clinique est allé à Sonia Marazzi, une Combattants Canada (ACC), Services de l'audiologie chez les adultes, de la faculté audiologiste respectée du the North Shore santé non assurés (SSNA), le Ministère de de médecine de l'université de Washington Children’s Hearing Clinic à Vancouver la défense nationale (MDN), la GRC et la à St. Louis, dans le Missouri. L'inscription Nord, en Colombie Britannique. Croix Bleue. Un rapport complet des en ligne au www.canadianaudiology.ca sera décisions et recommandations résultant de lancée le 1er décembre et l'espace sera La récipiendaire du Prix du mérite pour notre réunion sera publié sur la page Tiers limité. la présentation d'un poster en recherche payants de notre site web. exceptionnelle par un(e)étudiant(e) est Christine Turgeon de l'université de Une réunion supplémentaire s'est tenue Tom McFadden Montréal. Les autres gagnant(es), dont les avec le groupe SSNA le 30 septembre pour Directeur Exécutif candidatures ont été avancées par leurs discuter des plusieurs questions L'Académie écoles respectives, du Prix pour étudiant spécifiques au SSNA émanant des Canadienne sont: membres de l'ACA. d'Audiologie

• Emilie Gosselin, Université de Nous avons célébré dernièrement La Montréal semaine nationale de l'Audiologie (du • Bonnie Lampe, University of Western 18 au 24 Octobre, 2010). L'équipe Ontario marketing de l'ACA a produit une Trousse • Maxime Maheu, Université d'Ottawa d'outils Media en ligne pour assister les

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 9 2nd Annual Spring CAA Audiology Seminar

Saturday, April 2, 2011

Who Should Attend? Audiologists | Hearing Instrument Practitioners | Clinical & Private Practice | Students | Public Health

Featuring Michael Valente PhD. Director, Division of Adult Audiology Washington University School of Medicine St. Louis, Missouri, USA

For registration, program and hotel information go to: Delta Beauséjour Hotel, Moncton, NB www.canadianaudiology.ca www.deltabeausejour.com 1-800-264-5106 [email protected] audioLogY neWs |

Audiology History at The Canadian Hearing Society: 70 Years of Excellence

By Rex Banks, M.A.CCC-A, Reg. CASLPO; Director, Hearing Health Care; Chief Audiologist; The Canadian Hearing Society

he Canadian Hearing Society is the Alexander Fee, was retained as a medical hearing losses. Fast forward to 2010, Tlargest organization of its kind in consultant to CHS. Dr. Fee examined CHS audiologists are still concerned North America serving the needs of approximately 25% of all new clients, about this issue and are working with culturally Deaf, oral deaf, deafened, and administered functional tests with and researchers at The University of Toronto hard of hearing people across Ontario without hearing aids, and advised clients to study the relationship between the and Canada. as to possible benefit from treatment, stigma associated with hearing loss hearing aids, and lip-reading. and/or aging and how these social Often associated with advocacy issues Additionally, Dr. Fee also answered perceptions affect the adjustment of pertaining to the Deaf community, what inquires from distant points on behalf of hearing loss and the use of hearing aids many audiologists don’t know is that the society. since its inception in 1940, The In the 1950s, the first of many grants to Canadian Hearing Society has not only The Second World War had just ended subsidize hearing aids for children was embraced the field of audiology, but has and much of the work of the society was received and in 1952 CHS purchased its proven itself to be both a leader and focused on helping veterans who had first audiometer at a cost of $845. This innovator in the early days of the returned from war service with severe was a significant expenditure at the time audiology profession in Canada. Along hearing loss. CHS obtained a grant from but was deemed important and with establishing a national agency the Department of Veteran Affairs to necessary as CHS began exploring this concerning itself with jobs for Deaf and assist in providing amplification to 5,000 component of service. In 1962, a hard of hearing individuals, the deafened servicemen. At the very same “sound-proof room” and audiometer standardization and costs of hearing time and for the same reasons, the were installed at the “Head Office.” Two aids, rehabilitation of ex-servicemen and profession of audiology was in its infancy staff people were trained to administer the distribution of expertise and in the United States. Already, CHS’ sense hearing tests while the search for an information were key core components of the necessity of audiology was proving audiologist commenced; an ambitious of the original mandate of CHS – which to be cutting edge and revolutionary. undertaking as there were no Canadian was initially known as The National audiology training programs in existence Association for the Deaf and Hard of Hearing aids were a focus of the1947– at the time. Hearing 48 Annual Report. Dr. Fee described among his findings his patients’ In 1967 audiologist Errol Davis was To further these causes, in June of 1940, resistance to hearing aids, particularly in hired. He was the first audiologist in noted otologist of the time, Dr. G. the younger age groups with moderate Toronto and soon reorganized the

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 11 | AUDIOLOGY NEwS department into the most up-to-date helping establish the criteria for a Communicative Disorders Assistant audiological facility in Canada. The CHS governmental definition of deafness. (CDA) program at Georgian College. Audiology Department set the standard After the Minister of Health announced CHS’ audiology alumni list of for audiology clinics in teaching the details of the newly established volunteers, students and clinicians hospitals in Toronto and throughout the Assistive Device Program, CHS was boasts some of the most well-known province. contracted to provide expertise and audiologists in Canada. administration to the Hearing Aid From 1940 through the 1970s CHS Services Monitoring Board (later known Today, The Canadian Hearing Society conducted thousands of hearing aid as the Advisory Committee on Hearing employs a provincial network of audio- evaluations and continued to expand its Aid Services). logists approaching hearing health care Audiology and Hearing Aid Programs from a holistically minded point of view. along with the institution of a hearing In addition to audiological testing, CHS provides services, products and screening van, which was donated by hearing aid evaluations, electrophysio- information relating to hearing loss as IBM and equipped by The Lions Club logical assessment, aural rehabilitation, well as offering a wide-range of and hearing aid dispensing, in the 1980s complementary education and support In the early 1980s CHS supported the the program grew to provide a programs for both children and adults in regulation of audiologists in conjunction significant role in the education of the an accessible environment. The with OSLA and worked closely with professions of audiology and speech- Audiology Department remains integral what was then called The Association of language pathology. CHS became a to the fabric of CHS, touching virtually Hearing Aid Dispensers, responding to recognized training site for all university every department and affecting issues which arose from the Health audiology programs in Canada, the thousands consumers every year. Professions Legislation Review. CHS Speech-Language Pathology Program at audiologists were also involved in the University of Toronto and the

CANADIAN ACADEMY OF AUDIOLOGY 5160 Lampman Avenue, Burlington ON L7L 6K1 Tel.:905.319.6191 / 800.264.5106, Fax: 905.319.8563 Web: www.canadianaudiology.ca, Email: [email protected] BOARDOFDIRECTORS / CONSEIL DE DIRECTION

Rex Banks Susan Nelson-Oxford Calvin Staples Glynnis Tidball President / Presidente Secretary / Secrétaire Director / Directeur Director / Directrice Canadian Hearing Society Vancouver Island Health Authority Conestoga College St. Paul's Hospital Toronto, ON Victoria, BC Kitchener, ON Vancouver, BC

Victoria Lee Erica Wong Ronald Choquette Bill Campbell President-Elect / Présidente-Désignée Director / Directrice Director / Directeur Director / Directeur Provincial Auditory Outreach Program Mount Sinai Hospital Régie de la Santé du Restigouche Thunder Bay District Burnaby, BC Toronto, ON Campbellton, NB Health Unit Thunder Bay, ON Carri Johnson Bill Hodgetts Susan English-Thompson Past President / Présidente Sortant Director / Directeur Director / Directrice Near North Hearing Centre University of Alberta Sackville Hearing Centre Tom McFadden Executive Director / North Bay, ON Edmonton, AB Sackville, NS Directeur General Canadian Academy of Petra Smith Steve Aiken Jim Nelles Treasurer / Trésorière Director / Directeur Director / Directeur Audiology Hastings Hearing Centres Dalhousie University Connect Hearing Burlington, ON Landmark, MB Halifax, NS Vancouver, BC

12 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION audioLogY neWs |

Celebrating 40 Years of Academic Excellence in Audiology and Speech-Language Pathology at the University of western Ontario By JB Orange, PhD, Associate Professor and Director

he School of Communication Sciences and Disorders at Tthe University of Western Ontario (UWO), first established in 1970–1971 with its Founding Director Dr. James Stouffer, is celebrating its 40th anniversary during the 2010–2011 academic year. Current students, staff, and faculty, including alumnae/alumni and former staff and faculty, will be attending many of the several scholarly and social events planned over the course of the year to celebrate the school’s important milestone. Drs. Bob Harrison (left) and Richard Seewald at the gala dinner. The first and largest event was a combination scientific symposium and gala luncheon and dinner held at the UWO on Friday the October 1, 2010. Support for the day’s events came from the Daniel Ling Speaker Series Fund, the Faculty of Health Sciences at the UWO, The Harmonize for Speech Foundation, The School of Communication Sciences and Disorders, and the National Centre for Audiology. Over 125 alumnae/alumni, current students, local and regional clinicians and faculty attended half-day symposium sessions in audiology and speech-language pathology. Registrants heard Dr. Robert Harrison, from the University of Toronto and SickKids Hospital, speak at the Hearing Science Seminar on the topic of “Auditory System Development and Plasticity.” Dr. Ewan Macpherson on the bag-pipes. Others attended the Siemens Symposium led by Dr. Bill Hodgetts from the University of Alberta’s Department of Speech Pathology and Audiology on the subject of “Bone Conduction Amplification: Present and Future Considerations.” Other registrants attended the session titled “Recent Developments in Acquired Apraxia of Speech” given by Dr. Julie Wambaugh from the Department of Communication Sciences and Disorders at the University of Utah. Other delegates heard Drs. Lisa Archibald and Daniel Ansari, from our school and the Department of Psychology at the UWO, respectively, discuss the topics of “Numeracy and Arithmetic: The Roles of Development and Individuals Differences” and “The Psycho-educational Assessment from Mr. George Shields (left) and Mr. Cam Miller.

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London Men of A Chord. (left to right) Drs. Margaret Cheesman, Vijay Parsa, Scott Adams, Ruth Martin. a Speech and Language Perspective.” barbershop singing chorus who of the Canadian Association of Speech- The academic portion of the day ended honoured Cam and the school with Language Pathologists and Audiologists with tours of faculty members’ exquisite in-tune melodies sprinkled being held in Montreal in late April laboratories and individualized with comical interludes. Former 2011. Dr. Martin will address in her demonstrations of research activities. department/school co-directors Drs. session the latest empirical evidence Richard Seewald and Joseph Corcoran surrounding the concepts of The evening gala dinner, opened reminisced publically about their swallowing neuroplasticity and ceremoniously by the splendid bag- splendid time as co-directors. A efficacious approaches to rehabilitation piping of one of our faculty members PowerPoint slide show presentation, of dysphagia. Dr. Ewan Macpherson, was marked by assembled by a group of current the official renaming of four student student volunteers, contained photos of Careful reflection on the numerous and academic entrance and academic former and current faculty with cutting-edge academic, clinical and continuing awards in honour of Mr. decades-marking clothing, hair-dos, professional accomplishments of Cam Miller, a longstanding barbershop and eyeglasses and which ran students, alumnae/alumni, and faculty singer and trustee of the Harmonize for throughout the evening, yielding many from the school over the past 40 years Speech Fund. These awards will laughs and comments such as, “Oh my shows that there is much to celebrate henceforth bear Cam’s name. Cam goodness, is that ………!” and to acknowledge. Our graduates worked tirelessly for many decades as a and faculty have helped advance champion of our students, their Other planned events to mark the multiple scientific bases of foundational research, and the academic mission of School’s 40th Anniversary include Dr. knowledge related to hearing, our school. Special guests included Ewan Macpherson presenting at the speech, language, voice, cognitive- Cam and his wife Mary, Mr. George Annual Conference of the Canadian communication and swallowing Shields and Mrs. Gail Shields, where Academy of Audiology held in October disorders, and of innovative evidence- George is the chairman of the 2010 in Montreal. Dr. Macpherson’s based rehabilitation approaches. The Harmonize for Speech Fund. George talk addressed the importance of coming decades at the school will delivered a moving and eloquent multidimensional spatial sound cues undoubtedly lead to additional tribute to Cam, describing Cam’s for sound localization among exemplary leadership contributions boundless energy, enduring support, individuals with normal and impaired that will advance scholarly thinking and determined philanthropic focus on hearing. In addition, Dr. Ruth Martin, and clinician-scientist based practice those with speech, language, hearing, an award-winning neuroscientist and patterns in audiology and speech- and voice problems. During dinner, speech-language pathology faculty in language pathology. guests were serenaded by the London our school, will be our sponsored Men of A Chord, a close to 20 person speaker at the next Annual Conference

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Noise Cancelling Headphones

By Marshall Chasin, AuD, MSc, Aud(C), Reg. CASLPO

n 1933 the Journal of the Acoustical would cancel similar frequency sounds the listener. There is a practical limit ISociety of America published an article but where a trough met up with a wave when listening through headphones about using sound waves that were 180 crest. One could simply reverse the since the human ear is so small – degrees out of phase to “cancel” similar wires connecting the back of one of two typically one can obtain a 12 decibel sounds in the environment. That is, a loudspeakers and if there were oriented reduction but only below 1,000 Hz. sound would be generated that would correctly, the result would be a quieter This means that the loudness of the be identical to the noise it wanted to sound. Keele University in England was background noise can be reduced in suppress, but be the opposite phase – one of the first to have an installation half and only in the lower to middle as if an ocean wave peak met up with a like this. A large loudspeaker was portions of the piano. Since most wave trough going in the other placed on the roof of the mechanical background noise is in the lower to direction, the net effect would be engineering building and it generated middle portions of the piano, this momentary calmness. This is the basis an identical sound to that which was works quite nicely. And since this is of noise cancellation. constantly being emitted from the air more of a law of physics rather than exhaust system, but in opposite phase. engineering ingenuity, all noise Most unwanted background noise is The net result was a much quieter cancellation earphones are pretty much lower frequency – it has energy on the campus in the vicinity of the the same. One would be hard pressed left hand side of the piano keyboard mechanical engineering building. to say that a $200 set of noise and a feature of all lower frequency Jaguar cars, since the 1980s have had cancellation earphones would be any sounds is that it has a long wavelength noise cancellation loudspeakers better than a $20 pair. (typically over a meter long). Given the (sometimes called “anti-noise”) built technology of the middle part of the last into the exhaust system of their vehicles Recently noise cancellation has even century, it was a fairly simple task to and this makes for a quieter ride all been used in hearing aids where the generate low frequency sounds that round. annoying squeal that is sometimes heard (called feedback) is “cancelled” However, it wasn’t until the 1990s, with by the generation of the same feedback the increasing usage of digital squeal, but 180 degrees out of phase. technology, that noise cancellation was The hard of hearing person can now employed in personal headsets. With turn up the volume of their hearing aids digital technology it’s an even simpler further without being as limited by the task than switching the wires around on whistling. a loudspeaker. One simply needs to generate a noise but covert all Please feel free to copy and distribute information from + to − and add the this one-page information sheet and two together: +2−2 = 0. Noise distribute it to your clients courtesy the cancellation headsets have been very Canadian Academy of Audiology, useful to reduce the background noise Andrew John Publishing Inc., and and thereby provide more comfort for Canadian Hearing Report.

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Do ABRs Affect DPOAEs?

By Lendra Friesen, PhD, Sunnybrook Health Sciences Centre

voked otoacoustic emissions (OAEs) detecting subtle auditory dysfunction. primary signals (f1 and f2), with f2/f1 = Eare responses generated in the inner For example, several different studies 1.3, were generated with test frequencies ear to various types of stimuli and are have noted a decrease in DPOAE ranging from 5 to 25 kHz. A peak at 2f1- considered to be a byproduct of the amplitude without a corresponding f2 in the spectrum was accepted as a cochlear amplification that enhances permanent increase in ABR thresholds.2–4 DPOAE if it was 3 dB above the noise sensitivity and frequency selectivity. In addition to permanent changes, floor. DPOAEs were collected before, Clinically, the presence of distortion transient decreases in DPOAE levels immediately following, and one hour product otoacoustic emissions (DPOAEs) have also been described in response to after ABR analysis in all mice. is used to indicate healthy middle ear toxic sound stimuli. Studies in both and cochlear function, but does not humans and animals have shown In all strains of mice, results revealed that determine absolute threshold with detectable reduction in DPOAEs in the levels of the DPOAEs collected accuracy. DPOAEs are evoked using a response to a sustained and intense noise immediately following ABRs were pair of primary tones, f1 and f2 (where exposure.5–7 However, routine ABR significantly reduced compared to the f1 is greater than f2). The evoked testing has not been reported to impact pre-ABR DPOAEs. Also, the DPOAEs responses from these tones occur at DPOAEs. obtained one hour following ABR testing predictable frequencies, depending on f1 showed recovery of the responses in all and f2, and are known as distortion In the Mhatre et al. study,1 ABR varieties of mice and there was no products. A recent finding in mice has thresholds were recorded from the significant difference between DPOAEs revealed that the combined use of the vertex (non-inverted) to the ipsilateral collected pre-ABR and those obtained auditory brainstem response (ABR) and mastoid (inverted), with the contralateral one hour following ABR measurements. DPOAEs, carried out in succession, with mastoid as the ground in several the ABR preceding the DPOAEs, yields a different strains of mice. The hearing Superoxide radicals or reactive oxygen temporarily reduced DPOAE response.1 range of mice is from about 1 khz to 70 species (ROS) are elevated in noise Although the underlying mechanism of kHz. Therefore the tonebursts and clicks trauma and anti-oxidant treatment has the reduced DPOAE immediately used in this study were different from been shown to prevent hair cell damage following ABR measurement remains to those used clinically. Broadband clicks and hearing loss.8 Thus, Mhatre et al. be determined, these results have and tonebursts of 8, 16, 24, and 32 kHz investigated if excess production of ROS important clinical implications in were presented at a rate of 33 per second was responsible for the post-ABR situations where both the ABR and and responses were averaged over 500 DPOAE reduction. Specifically, the study DPOAEs are assessed. trials. Testing began at 85 dB SPL and tested if excess SOD1 expression can was sequentially attenuated in 5 dB steps prevent DPOAE reduction immediately DPOAEs provide a sensitive measure of until threshold level was reached. In following ABR measurement in SOD1 outer hair cell function. They have been DPOAE testing, low level primary signals transgenic mice. SOD1 is a cytoplasmic shown to be more sensitive than ABRs in (L1 = 65 dB SPL, L2 = 50 dB SPL) enzyme critical in neutralizing oxygen

16 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | radicals and a major regulator of ROS preceding ABR assess-ment, and thereby Modification of otoacoustic emissions levels within cells. The transgenic mice ensuring the DPOAE response is following ear-level exposure to MP3 overexpress SOD1 nearly three-fold unaffected. If ABR measurements are to player music. Int J Audiol greater than their wild type (typically precede OAE evaluations, then a 2008;47(12):751–60. occurring in nature) littermates.9 Similar minimum interval of two hours is 6. Korres GS, Balatsouras DG, to their wild type littermates, the SOD1 recommended between these tests. Tzagaroulakis A, Kandiloros D, transgenic mice also demonstrated post- Ferekidou E, and Korres, S.. ABR DPOAE reduction, and thus did REFERENCES Distortion product otoacoustic not support a role for superoxide 1. Mhatre AN, Tajudeen B, Welt EM, emissions in an industrial setting. radicals in transient reduction of DPOAE Wartmann C, Long GR, Lalwani Noise Health 2009;11(43):103–10. AK. Temporary reduction of 7. Muller J and Janssen T. Impact of The authors speculate that the distortion product otoacoustic occupational noise on pure-tone amplitude reduction induced by the emissions (DPOAEs) immediately threshold and distortion product preceding ABR analysis may reflect a following auditory brainstem otoacoustic emissions after one work- direct effect on the mechanosensory hair response (ABR). Hear Res day. Hear Res 2008;246(1-2):9–22. cells in response to continuous auditory 1010;269(1–2): 180–85. 8. Henderson D, Bielefeld EC, Harris stimulation. Alternatively, several studies 2. Desai A, Reed D, Cheyne A, Richards KC, and Hu BH. The role of oxidative have shown that activation of the medial S, and Prasher D. Absence of stress in noise-induced hearing loss. olivocochlear neurons leads to reduction otoacoustic emissions in subjects with Ear Hear 2006;27(1);1–19. of DPOAEs.10,11 Therefore, the ABR normal audiometric thresholds 9. Coling DE, Yu KC, Somand D, et al. stimuli might activate the medial implies exposure to noise. Noise Effect of SOD1 overexpression on olivocochlear neurons that suppress the Health 1999;1(2):58–65. age- and noise-related hearing loss. outer hair cells and their OAEs. Another 3. Lapsley Miller JA, Marshall L, and Free Radic Biol Med 2003;34(7):873–80. cause of the reduction might be the Heller LM. A longitudinal study of 10. Liberman MC. Rapid assessment of activation of the middle ear muscle changes in evoked otoacoustic sound-evoked olivocochlear reflex. This activation results in emissions and pure-tone thresholds feedback: suppression of compound stapedius muscle contraction, which as measured in a hearing conservation action potential by contralateral alters the sound pressure in the ear program. Int J Audiol sound. Hear Res 1989;38:47–56. canal, yielding a reduced response by 2004;43(6):307–22. 11. Liberman MC, Puria S, Guinan JJ Jr. the outer hair cell. 4. Lapsley Miller JA, Marshall L, Heller The ipsilaterally evoked olivocochlear LM, and Hughes LM. Low-level reflex causes rapid adaptation of the In conclusion, a practical outcome of otoacoustic emissions may predict 2f1-f2 distortion product otoacoustic this study is the authors’ recomm- susceptibility to noise-induced emission. J Acoust Soc Am endation for the reversal of the auditory hearing loss. J Acoust Soc Am 1996;99(6):3572–84. test order when assaying both ABR and 2006;120(1):280–96. OAEs, with the OAE measurements 5. Bhagat SP and Davis AM.

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Unmasked Thresholds and Minimum Masking in Infants and Adults: A Timeline for Separating Sensory from Nonsensory Contributions to Infant-Adult Differences in Behavioural Thresholds

Student: ABSTRACT Isabelle-Anne Pleau The objective of the present research project is to extend results from a previous study by Supervisor: Nozza and Henson (1999) to a slightly older infant population. In the aforementioned study, André Marcoux, PhD it was demonstrated that infant unmasked thresholds differed from those of adults, and that a difference in minimum effective masking as a function of age and frequency was present. The conclusions from this study were that while infants’ hearing thresholds were not significantly higher than adults, infants’ threshold were increased by non-sensory factors such as fatigue and lack of concentration. Their sample of participants consisted of a group of 23 infants (M = 7.9 months, R = 6.7 - 9.4 months) and a group of 24 adults. A major flaw from the Nozza and Henson study was that the influence on test signals by the outer ear were not considered and hence values collected were biased by the fact that measurement equipments were calibrated for adult outer ears only. We are proposing an extension to the Nozza and Henson (1999) experiment to control for outer ear characteristics and determine whether there is indeed a difference in sensory status between infants and adults. The Minimal Masking Level technique used in Nozza and Henson will again be used to negate the influence of non-sensory factors commonly observed in infants. Also, the current study will look more precisely for a time course of the maturation of sensory abilities. Results from this study will help determine whether correction factors which highlight sensory immaturity must be applied to hearing threshold values obtained in infants when compared to audiometric reference values (i.e. normalized for the adult population). This will increase the accuracy of diagnoses for infants. Hearing-impaired infants are the most likely to benefit from this accuracy as treatment plans are defined based on hearing threshold data.

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Users’ Perspectives on the Benefits of FM Systems with Cochlear Implants

ABSTRACT This study explored: (1) the benefits of an FM system in real-world environments from the perspective of adults with cochlear implants, and (2) the factors and barriers to using an FM system with a cochlear implant. Using a qualitative research design, 14 adults with unilateral cochlear implants recorded their experiences during a two-month trial period with a personal FM system and responded to a questionnaire at the end of the trial. A detailed analysis of 169 journal entries (230 hours of FM use) permitted a description of the benefits and negative aspects associated with FM use in everyday listening environments. The primary benefits were related to improved access to and quality of sound, improved distance listening, ease of listening, and better social integration. Negative perceptions were associated with the equipment both with regard to physical aspects and adjustments. In addition, technical, individual, social, and environmental factors were Student: identified that can influence the user’s decision to use the FM device. Questionnaire Philippe Fournier responses indicated that the majority of individuals rated the FM system as somewhat or Supervisor: very helpful. The findings suggest that FM systems can improve communication in everyday Elizabeth Fitzpatrick, PhD listening environments for some adults with cochlear implants.

peer reviewed

Revue canadienne d’audition Canadian Hearing Report: Call for Reviewers Canadian Hearing Report is published six times per year and is the official publication of the Canadian Academy of Audiology (CAA). CHR is pleased to offer peer reviewing to all interested authors who submit manuscripts to the journal. To carry out this process, the editorial board of Canadian Hearing Report is currently assembling a group of volunteer peer reviewers. We are looking for dynamic experts in various fields of audiology to serve on our peer-review panel. The list of the peer reviewers will be published annually in the journal. The manuscripts would be sent and received via email. If you are interested in becoming a peer reviewer for CHR, please contact Marshall Chasin ([email protected]), editor- in-chief to discuss your particular area of expertise.

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peer reviewed

Examination of the Associations between Cardiovascular Health and Hearing: Comparative and Historical Perspectives

By Kathleen M. Hutchinson, PhD and Helaine M. Alessio, PhD

About the Authors

Kathleen M. Hutchinson (far left) is with the Department of Speech Pathology and Audiology, Miami University Oxford, OH USA. She can be contacted by e-mail at: [email protected].

Helaine M. Alessio is with the Department of Kinesiology and Health, Miami University Oxford, OH USA

ABSTRACT

Purpose: Recent evidence has revised popular views about age-associated hearing loss, and has uncovered variables other than age that play a significant role in the decline in sensory function over time. The purpose of this review is to describe a quarter century of progress in understanding factors, other than age, that are associated with presbycusis, focusing on the influence of cardiovascular health.

Methods: Scientific evidence investigating noise exposure, cardiovascular health, personality, and other health variables was critically examined in this literature review.

Results: Over 25 years of research investigating hearing loss over time indicates that although aging plays a part, multiple factors, and in particular, cardiovascular health, impacts the rate and age at which hearing sensitivity is compromised and presbycusis occurs.

Conclusions: Factors other than age contribute to hearing sensitivity, opposing the long- standing expectation that hearing loss declines with age. Cardiovascular health is a powerful mediator of hearing sensitivity and individuals with high cardiovascular fitness can maintain better hearing acuity well into adulthood.

ccording to the Canadian sociodemographic factors such as interpersonal relations, and lead to ACommunity Health Survey and the marital status, education, and income depression. Because the number of older National Population Health Survey, did not matter, except that hearing loss adults is expected to double in size over hearing impairment is a common was more common among men.1 the next 20 years, and will represent chronic condition in later life. In both Hearing loss interferes with effective roughly 20% of the United States Canadian studies, the prevalence of communication, may disrupt work population,2 the preservation of hearing hearing loss increased with age and performance, compromise safety, impact is a national health concern. Already, the

20 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | number of people in the world, ages 65 exposure. Hearing thresholds typically perceptual hearing loss of Mabaan adults and older, increases at an average rate of recover from TTS after brief noise over 60 years of age is indistinguishable 870,000 each month. exposure. While intensity, duration, and from young adolescents suggests a frequency of noise exposure are key correlation between auditory capabilities Presbycusis is a peripheral and/or central determinants of this phenomenon, other and the healthy and active lifestyle of the auditory decrement over time.3 For factors independent of these noise Mabaan people.10 Many people who live years, hearing loss was expected to characteristics may also influence this in industrialized countries are exposed decline with age, starting at around age effect. For example, underlying to environmental noise unfamiliar to the 30. It is well known that noise exposure correlates such as psychological Mabaans and do not typically live active accelerates the loss of hearing acuity and profiles,4 body temperature,5 physical lives that include regular harvesting and after varying periods of time, causes a exercise,6 and variations in middle ear hunting. Despite the typical industrial, permanent noise-induced hearing loss. impedance and acoustic reflex musical, entertainment, and motorized Additionally, a common finding is the properties7 have been shown to sounds, noise exposure is moderated in great individual variation in hearing influence susceptibility to TTS. A most developed countries through work change among older adults of the same reduction of blood flow through the regulations, educational efforts, and age. However, studies of different inner ear as a result of generalized safety precautions including mufflers cultures and cohorts have shown that peripheral vasoconstriction which and earplugs required in noisy depending on where and when one lives occurs in response to loud noise may workplaces. Additionally, many people often determines the amount of noise also be an underlying determinant of use hearing protection during routine exposure and hearing loss. Recent TTS.8 The cardiovascular system is activities (e.g., lawn mowing) that experiments have reported that hearing believed to play a significant role in involve loud noise. loss is caused by the general effects of a regulating hearing sensitivity. Current variety of factors,4 some within and some concepts in auditory physiology include In contrast, recent popularity of listening outside of a person’s control. For active mechanisms that serve to to music via ear bud headphones has example, the presence or absence of counteract the effects of trauma and caused young individuals to suffer regulatory legislation requiring the stress. The effect of simultaneous noise premature hearing loss, resulting in reduction of noise exposure in the exposure and cardiovascular responses hearing sensitivity levels equivalent to workplace, individual access to hearing to exercise has come under scrutiny in individuals who are decades older.11 protective equipment, use of ear bud both leisure and work environments. Exposure to noise through music headphones, or even knowledge about This review begins with a discussion of performance is another potential the consequences of noise exposure, underlying correlates of permanent mediating factor that contributes to may influence both the amount of noise hearing loss in addition to the role of hearing loss. Axelsson and Lindgren12 and behaviour that ultimately affect cardiovascular health in regulating found that pure tone thresholds among hearing conservation.4 hearing sensitivity, first reported by 59 of the 139 musicians tested showed Alessio and Hutchinson in 1991.9 more hearing loss than would be METHODS expected with age, worsening at age 60. Primary sources from peer-reviewed ENVIRONMENTAL NOISE Similarly DiSalvo13 and Deatheradge14 literature investigating multiple factors The effect of environmental noise, investigated hearing sensitivity among associated with presbycusis and noise- referred to as sociocusis, is known to 33 younger instrumentalists and induced hearing loss were consulted in influence the progression of presbycusis vocalists and found no definitive this review. Assessment of hearing depending on the amount of time and evidence indicating whether a young sensitivity focuses on pure tone level of noise exposure at work, leisure adult who plays a musical instrument or threshold (PTT) and temporary or home settings. In some settings, spends considerable time exposed to threshold shift (TTS). PTT is considered sociocusis is negligible. For example, music has a greater risk of hearing loss an objective criterion to establish hearing loss is rare in Mabaans, a compared to a group of 33 non- hearing ability based on a person’s population indigenous to central Africa, musicians. Physical fitness levels were response to pure tone stimuli at different where individuals have little to no similar in both groups and results frequencies. TTS is a short-term hearing exposure to industrial noise in this area included only young adults. decrement caused by brief noise of Southeast Sudan. The fact that the Nevertheless, the use of specialized

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 21 | earplugs by professional musicians may assist in protecting A 25 hearing sensitivity, especially over time. Coronary-Prone

Not Prone GENETICS 20 Hearing loss results from a number of causes and can be characterized as congenital or acquired. Approximately six of every 1,000 newborns have a significant hearing problem 15 at birth, and more than 4,000 babies are born with hearing loss each year.2 Advances in genetics have led to the 10 identification of genes that cause hearing loss; as many as loss (dB) Hearing half of individuals with hearing loss may have a genetic 5 origin. For example, the connexin 26 (CX26) genetic disorder causes disruption of potassium flow in the inner ear 0 with subsequent hearing loss.15 Genetic factors play a major 2000 2500 3000 role in onset and progression of hearing loss, susceptibility Frequency to hearing loss due to noise exposure, and responsiveness to intervention, although the environment and disease processes may contribute to the degree and severity of B hearing loss.15 12

BEHAVIOURAL FACTORS

A common finding in audiology research is that the same 7 noise exposure may result in different levels of either temporary or permanent threshold shifts among similar-aged individuals. This variability complicates the ability to draw Hearing loss (dB) Hearing 2 conclusions about a cause-and-effect of noise and hearing loss. A study by Ickes et al.16 on stress reaction indicated that individuals who had higher intensive reactions to stress -3 ended up with prolonged peripheral blood vessel 2000 2500 3000 constriction, which in turn may have reduced blood Frequency circulation in the inner ear. When sorted into type A (coronary-prone) and type B (non-coronary prone) personality types, and exposed to 100 dB SPL noise, type A C 30 persons demonstrated increased vasoconstriction compared with persons categorized as type B. Without direct 25 measurements of hearing sensitivity, the authors of this study could only hypothesize that the effects of prolonged 20 vasoconstriction in type A would likely result in higher risk 15 for TTS. 10 17 TTS and blood pressure were assessed by Dengerink et al. loss (dB) Hearing 5 who concluded that hearing sensitivity was related to an individual’s general stress response to noise. The link 0 2000 2500 3000 between personality and hearing sensitivity appeared to be Frequency mediated by blood pressure and circulation. Hutchinson and Alessio18 investigated the interaction of personality, noise, and hearing sensitivity with a group of individuals Figure 1 Hearing levels in dB HL at 2000, 2500, and 3000 Hz in coronary- categorized as coronary prone, according to the Myers-Briggs prone and noncoronary-prone groups following 10 minutes of noise (A), test, which consistently identifies sensing/judging (SJ) pre- exercise only (B), and noise and exercise (C).

22 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | ferences within the type A behaviour EXERCISE: ACUTE VERSUS Shortly after Saxon and Dahle’s 1971 complex. When compared with a CHRONIC publication, Ismail et al.20 investigated control group of noncoronary-prone Study of the effects of exercise on hearing the impact of chronic exercise on hearing individuals, the coronary prone group sensitivity, has produced intriguing sensitivity. Sixty-four adults between 23 had worse hearing levels at 2000 Hz results over the years. In 1971 Saxon and and 62 years of age took part in an eight- following 10 minutes of noise (13.7 ± Dahle19 tested a traditional activation month study. After measuring 5.1 vs. 6.5 ± 2.4 dB) and following 10 theory by assessing auditory thresholds cardiovascular fitness levels, 54 of the 64 minutes of noise accompanied by at 1000 Hz during rest and following a adults were equally divided into low, exercise (19.7 ± 4.4 vs. 7.4 ± 2.4 dB; p < stressor. The authors chose acute medium, or high physical fitness .05). Evidence of TTS following either exercise, which consisted of a 2.5 minute categories and 10 control subjects were noise or noise and exercise in the step test, as the stressor. They reported also sorted into an appropriate fitness coronary-prone group occurred that auditory threshold sensitivity was group. Then, over eight months, the independently of differences in significantly reduced following exercise- experimental group participated in circulatory and heart rate measures induced high heart rate compared with thrice-weekly hour-long supervised compared with a control group, rest; supporting a contention that acute conditioning activities, which included indicating other stress mechanisms and intense arousal impairs hearing 20 minutes of calisthenics followed by besides cardiovascular reactivity that sensitivity. This study was the first to running, and team sports, according to contribute to temporary hearing loss recognize a relation between cardio- individual preferences. Before and (Figure 1). vascular adjustments to acute exercise following the conditioning program, and hearing loss. PTT, and TTS following noise exposure

A B C 40% Systolic Blood Pressure Noise-only 74 40% Heart Rate 140 40% Systolic Blood Pressure Exercise-onl 160 73 130 140 Noise-Exerc 120 72 120 110 71 100 100 ) 70 -1 90 80 Noise-only Noise-only SBP (mm Hg) 80 60 69 Exercise-only 70 Exercise-only 40 68 HR (beats • mm SBP (mm Hg) 60 Noise-Exercise 20 Noise-Exercise 67 50 0 40 0 5 10 0 5 10 66 0 5 10 Minutes Minutes Minutes

70% Diastolic Blodd Pressure 70% Heart Rate 74 200 200 70% Systolic Blood Pressure 73 180 180 160 72 160 ) 140 71 -1 140 Noise-only 120 70 120 100 Exercise-only Noise-only 80 Noise-only DBP (mm Hg) 69 100 Noise-Exercise 60 HR (beats•min 80 Exercise-only Exercise-only 68 40 SBP (mm Hg) 67 60 Noise-Exercise 20 Noise-Exercise 0 66 40 0 5 10 0 5 10 0 5 10 Minutes Minutes Minutes Figure 2. Systolic blood pressure (SBP) during 40% and 70% of VO2 max with and without noise (A), Diastolic blood pressure (DBP) during 40% and 70% exercise with and without noise (B), Heart rate (HR) during 40% and 70% exercise with and without noise (C).

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A 40 were compared in all individuals as well as a number of health- related physio-logical variables. Results from Ismail’s study 30 indicated that chronic exercise was successful in improving biomarkers of cardiovascular fitness, including percent lean body 20 weight, resting, submaximal, and maximal heart rate. Maximum

Mean PT 1000 Hz Mean oxygen uptake (VO2 max) the benchmark assessment for cardio- 10 vascular health and fitness, also improved 21% after 8 months of participating in regular exercise. In contrast, the control group 0 reported no changes in any health-related variables after eight months. Although pure tone thresholds did not improve in the High Medium Low

Fitness Category experimental group, individuals in the experimental group were B 40 Age Classification less susceptible to temporary threshold shifts, indicating that the Youth Middle individuals who exercised recovered faster from auditory fatigue Young Older

30 following the eight-month conditioning program. This was the first report that associated cardiovascular fitness with enhanced auditory function. 20

Mean PT 2000 Hz Mean The beneficial role of exercise in mediating hearing sensitivity 10 was questioned in a 1981 study. Sanden and Axelsson21 reported temporary hearing loss in young adults who exercised for 10 0 minutes at 40% of VO2 max while simultaneously listening to High Medium Low 104 dB SPL noise. The authors hypothesized that elevated blood

Fitness Category temperature associated with acute exercise compromised C 40 cochlear reserve and function and caused TTS. The authors cautioned against participating in aerobic exercise activity that

30 included vigorous and bouncy movements accompanied by loud music, by placing blame on the exercise activity more than the

20 noise exposure. The same caution appeared in a brief magazine

Mean PT 3000 Hz Mean report by Navarro,warning readers of the risk of hearing loss

10 from exercising to loud music. The Sanden and Axelsson study and brief report by Navarro both referred to the potential harm

0 from combining vigorous exercise and noise exposure, but surprisingly, both considered exercise rather than noise to be the High Medium Low cause of hearing loss. Fitness Category

D 40 Hutchinson and Alessio23 questioned the assertion that either PTT or TTS could be influenced by noise combined with 30 exercise and physiological responses to exercise, regardless how vigorous, to a greater extent than actual noise exposure. They 20 compared the effect of low (40% of VO2 max) and high (70% of

Mean PT 4000 Hz Mean VO2 max) intensity exercise with and without 104 dB SPL of 10 noise on TTS. Figure 2 shows that heart rate, blood pressure, and core temperature increased in proportion to exercise 0 intensity and were not changed above resting levels by noise exposure alone23–25 TTS occurred following noise exposure only, High Medium Low with and without exercise of either intensity. These results Fitness Category Figures 3A–D. Mean pure tone threshold (PTT) at 1000, 2000, 3000, refuted Sanden and Axelsson and Navarro’s concerns that and 4000 Hz (± SD) in dB HL by fitness level and age classification. exercise contributes to temporary hearing loss when performed The population was separated into four age groups: 10–19, 20–27, 28– with noise exposure. 48, and 49–78 years, each of similar group size.

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Hutchinson and Alessio noticed a Table 1. Characteristics of four subject groups (mean ± SEM) comparing effects of surprising trend among participants in muscle strength and cardiovascular fitness on pure tone threshold the early studies (1991, 1992, 1994, and 1996): the more physically fit subjects VO2 tended to perform better on the - audiology tests than less physically fit subjects. This finding led to further investigations of hearing sensitivity among low, medium, and highly fit adults. Results indicated that high cardiovascular fitness correlated with better hearing sensitivity while low cardiovascular fitness correlated with worse hearing sensitivity.25–28 These findings (Figure 3) were particularly *Significant difference (p<.05) between Low CV-High MS and Low CV-Low MS and High CV-Low MS. evident among adults, age 50 and older, **Significant difference (p<.05) between both groups with low CV and both groups with high CV. † indicating that cardiovascular (CV) Significant difference (p<.05) between low CV-high MS and other three groups. †† Significant difference (p<.05) between low CV-low MS and high CV-low MS and high CV-high MS. fitness may have a protective effect on hearing loss with age.27, 28 Other health factors related to CV fitness and health especially of the stria vascularis. underwent skin fold testing, testing for were similarly examined in relation to Reduction in blood circulation through blood lipids and glucose, and a 48-hour hearing sensitivity, including muscle the inner ear can also cause reduced diet and physical activity recall. strength and blood pressure. Only CV hearing acuity over time and lead to TTS Distortion product otoacoustic health remained as a positive predictor and permanent hearing loss. Metabolism emissions (DPOAE) testing was per- of improved hearing sensitivity across and blood flow are directly related to the formed to assess cochlear integrity. age levels. vascular pattern of the cochlea. If one’s Baseline PTTs were also determined. circulation is compromised, blood flow The cardiovascular system has been through the cochlea may also be Participants in the study were split into found to play a crucial role in regulating reduced. The impact of the cardio- four groups for comparison, based upon hearing sensitivity. TTS, a short term vascular system on hearing sensitivity is their level of cardiovascular (CV) fitness worsening of hearing thresholds, results therefore theorized to be related to and muscle strength (MS): low CV-low from noise exposure; chronic noise changes in blood circulation to the MS, high CV-low MS, low CV-high MS, exposure may result in PTS. One widely hearing mechanism as a result of and high CV-high MS (Table 1). As held theory is that a reduction in blood exercise; it is hypothesized that regular expected, the group with both high CV flow through the inner ear causes exercise reduces PTS by an increase in and high MS had the best hearing temporary TTS and subsequent short- blood flow and oxygen delivery in a sensitivity. The group exhibiting the term hearing loss. Generalized healthy cardiovascular system. worst hearing sensitivity was the low CV peripheral vasoconstriction, which fitness and high MS group. Equally occurs in response to loud noise, may be Additional descriptive information surprising was the finding that that an underlying determinant of TTS.8 about the association between hearing when muscular strength was Variations in cochlear blood flow may sensitivity and health-related com- accompanied by high cardiovascular affect the availability of oxygen and ponents was studied by examining fitness, individuals demonstrated better glucose, which is more rapidly combined muscle strength and cardio- PTTs; high muscular strength alone was metabolized during sound stimulation.6 vascular fitness.26 Muscle strength was negatively correlated with PTTs.26 Once A decline in blood flow through the determined by performing leg curls, leg again, hearing sensitivity was associated inner ear is attributed to increased extensions, and bench press on a with cardiovascular health. It is unclear peripheral blood pressure or decreased Nautilus machine (Nautilus Inc., why muscle strength has a negative oxygen tension in the cochlear Deland, Fl) and a hand grip using a correlation with hearing sensitivity. endolymph and vasoconstriction, standard dynamometer. Subjects also Nevertheless, as long as high muscle

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A 12 Pre-training B 12 Pre-training Post-training 10 Post-training 10

8 8

6 * 6 * * Hearing loss (dB) Hearing 4 *

Hearing loss (dB) Hearing 4 * *

2 2

0 0 2000 3000 4000 2000 3000 4000 Frequency Frequency

Figure 4. Temporary threshold shift in dB HL pre- and post-exercise training for experimental group (A) that exercised (*p < .05) and control group (B). strength was combined with high level of hearing loss from noise at some frequencies (Figure 5). This cardiovascular fitness, then hearing exposure, thus preserving hearing increase in VO2 peak was similar to the sensitivity was better. sensitivity.29 By comparing hearing increase reported by Ismail et al.20 ability among low and moderately fit Although results suggest that exercise EFFECTS OF EXERCISE TRAINING people before and after the completion training may be used as a preservative ON HEARING ABILITY of an eight-week aerobic exercise measure against loss in hearing 25 Although cardiovascular responses to training program, Cristell et al. found sensitivity the increased in VO2 peak exercise in combination with noise do that an increase in cardiovascular fitness must achieve at least a level of fitness not appear to influence the level of (15–25% increase in VO2 peak) resulted considered to be moderate. In our hearing sensitivity,23–25 findings indicate in less susceptibility to TTS at all laboratory, low fit individuals who that chronic cardiovascular adaptations frequencies (Figure 4) and an improved their VO2 peak, but still did to physical training might attenuate the improvement in baseline hearing levels not attain a level of fitness that met or

A 4.5 B Pre-training 1.4 4 Post-training 1.2 3.5 1 3 0.8 Hearing loss (dB) Hearing 2.5 0.6

2 0.4 0.2 1.5 0 * Hearing Level (dB) Level Hearing 1 -0.2 0.5 * * -0.4 0 2000 3000 4000 -0.6 2000 3000 4000 Frequency Frequency

Figure 5. Pure tone thresholds in dB HL pre- and post-exercise training for experimental group (A) that exercised (*p < .05) and (B) control group.

26 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | exceeded moderate fitness level for their In a similar study, PTTs and distortion Alessio (1998, 2000, 2005, and 2010) age group, did not demonstrate product otoacoustic emissions (DPOAE) demonstrating the positive benefits of improved hearing sensitivity. measures were evaluated in a cardiovascular health on hearing representative sample of over 100 sensitivity among adults. Furthermore, CROSS-SECTION STUDY OF participants.28 DPOAE testing was these results are particularly strong CARDIOVASCULAR HEALTH ON performed in this study in addition to among aging populations; cardio- HEARING SENSITIVITY pure-tone threshold testing, as it allowed vascular fitness seemingly acts as a As demonstrated throughout this review, the researchers to obtain information mechanism of preservation for hearing while declining PTTs is considered a regarding cochlear function and sensitivity. normal age-related change, other factors, integrity. Similar to the previous study, such as cardiovascular health, can play VO2 peak was used to determine the HEARING LOSS AND DIABETES a role in the rate and intensity of these level of cardiovascular fitness; heart rate Given the microvascular abnormalities changes and may even conserve hearing response, blood pressure, and that underlie cardiovascular health and at some frequencies. Hutchinson and respiratory gases were monitored disease, it is reasonable to postulate that Alessio et al.27confirmed these findings throughout the test. After data similar mechanisms associated with in two studies, the first of which collection, participants were split into diabetes, particularly type 2 diabetes, examined the results of baseline PTTs four age categories containing 22 to 26 may be associated with hearing loss. and VO2 peak determination using a participants for analytic purposes Type 2 diabetes is the most common maximal or submaximal graded exercise (youth, 10 to 19 years; young, 20 to 27 form of diabetes. In type 2 diabetes, the test on a Monark bicycle ergometer. years; middle, 28 to 48 years; older, 49 cells do not recognize insulin and since Heart rate and blood pressure were also to 78 years). Multivariate analysis using insulin’s main role is to facilitate the taken during testing. At 2000 Hz, 3000 the fitness level as a factor (i.e., VO2 transfer of glucose from blood into cells, Hz, and 4000 Hz, pure-tone hearing was peak), and PTTs as dependent variables diabetics are at risk of being deprived of positively influenced by cardiovascular indicated significantly better thresholds glucose that can be used by cells for fitness. The variable, Decade* VO2 peak, for the high versus low fit participants at energy. If this happens, glucose builds which relates to the effect of one’s age 1000 Hz. Although PTTs worsened in up in the blood instead of going into and health on overall hearing, was persons in all cardiovascular fitness cells, and this leads to a number of statistically significant (p<.01), suggesting categories with age, multivariate ANOVA diabetic complications including a difference in hearing for differing levels performed using both age and fitness hypertension, heart attacks, and kidney of VO2 peak in relation to age. Data level as factors showed that those with failure. Whether or not the suggests that age 50 is the separation low cardiovascular fitness in the old age microvascular changes that occur in point, after which fitness level and age group had significantly worse pure-tone diabetics may be associated with are related in a statistically significant hearing at 2000 and 4000 Hz.28 The microvascular changes that influence way, with high fitness being positively PTTs of the old high fit group were hearing loss, has been examined in related to better hearing sensitivity consistently better than the mean several large scale studies. In a five-year (Table 2). Across the age groups, people thresholds of the low fitness levels in the population-based survey in Australia, with low cardiovascular health exhibited same age group. These results confirm age-related hearing loss was present in the worst hearing thresholds.12 previous studies by Hutchinson and 50% of diabetic participants (n = 210) compared with 38.2% of non-diabetic participants (n = 1,648) after adjusting Table 2. Pure tone hearing levels in dB HL by decade age groups, fitness level and for multiple risk factors.30 A large scale frequency cross-sectional study was used to examine the secular change of the prevalence of hearing impairment over three decades in US adults with and without diabetes. After adjustment for age, sex, race, and education, the prevalence of hearing impairment in the National Health and Nutrition

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Examination Surveys (NHANES) 1 muscle strength and high cardiovascular 4. Gates G and Cooper A. Incidence of (1971–1973) and 2 (1999–2004), fitness was associated with the most hearing decline in elderly. Acta respectively, was 24.4% and 22.3% for sensitive hearing. When cardiovascular Otolaryngol 1991;111:240–48. adults without diabetes compared with fitness is improved in lower fit adults, 5. Ickes WK, Espili J, Glorig AM. 28.5% and 34.4% for adults with hearing sensitivity also improves, yet the Pattern A personality and noise- diabetes. The results indicated that improvement has to reach a level of induced vasoconstriction. J Speech persons with diabetes have a higher fitness considered as moderate or higher. Hear Res 1979;22:334–42. prevalence of hearing impairment than When exercising to music, any 6. Dengerink JE, Dengerink HA, and persons without diabetes.31 temporary hearing loss that may occur Chermak GD. Personality and is due to the level of noise and is not vascular responses as predictors of The link between diabetes and hearing exacerbated by the exercise. After age temporary threshold shifts after loss was investigated further in order to 50, individuals with high cardiovascular noise exposure. Ear Hear determine possible causal factors. In the fitness experienced significantly better 1982;34:196–201. National Health and Nutrition hearing sensitivity than low fit 7. Lindgren F and Axelsson A. The Examination Survey (NHANES) study, individuals, who demonstrated a typical influence of physical exercise on 1,508 participants, aged 40–69 years, age-associated decline in hearing. susceptibility to noise induced who completed audiometric testing Evidence suggests that a personality type temporary threshold shift. Scand during 1999–2004 were studied to affiliated with coronary prone behaviour Audiol 1988;17:11–17. determine whether controlling for is associated with compromised hearing. 8. Borg E. A quantitative study of the vascular or neuropathic conditions, Twenty-five years of research supports effect of the acoustic stapedius reflex cardiovascular risk factors, glycemia, or the importance of health and lifestyle in on sound transmission through the inflammation influenced the association maintaining hearing sensitivity over the middle ear of man. Acta between diabetes and hearing sensitivity. life span. Otolaryngol 1968;66:461–72. Bainbridge et al (2010) concluded that 9. Contrada RJ, Glass DC, Kakoff LR, mechanisms related to neuropathic or ACKNOWLEDGEMENTS et al. Effects of control over aversive microvascular factors, inflammation, or The authors acknowledge Anita stimulation and Type A behavior on hyperglycemia mediate the association Sackenheim for preparation of the cardiovascular and plasma of diabetes and hearing impairment.32 manuscript and the Miami University catecholamine responses. Summers Scholars program for support Psychophysiology 1982;19:408–19. CONCLUSION of undergraduate research. 10. Alessio HM and Hutchinson KM. This review has described the Effects of submaximal exercise and chronological progression of research on CONFLICTS noise exposure on hearing loss. Res major factors, other than age, that None declared. Quarter Exerc Sports 1991; influence hearing sensitivity. The 62:413–9. incidence of hearing loss may increase REFERENCES 11. Rosen F. Epidemiology of hearing with age in many parts of the world; 1. Corna LM, Wade TJ, Streiner DL, loss. Internat J Audiol 1969;8:260– however, presbycusis does not occur in and Cairney J. Corrected and 77. all persons at one particular age point. uncorrected hearing impairment in 12. Brant LJ, Gordon-Salant S, Pearson When exposed to noise, temporary older Canadians. Gerontology JD, et al. Risk factors related to age- hearing loss typically occurs regardless 2009;55:468–76. associated hearing loss in the speech of age; yet factors other than age 2. U.S. Census Bureau. National frequencies. J Am Audiol Assoc significantly influence one’s hearing population projections. 2010. 1996;7:152–60. sensitivity. Compared to lower fit Retreived July 14 from: 12. Axelsson A, Lindgren F. Hearing in individuals, TTS recovery is much http://www.census.gov/population/ classical musicians. Acta Oto- quicker in moderate and high fit www/pop-profile/natproj.html. Laryngol 1981:Supp 377:3–74. individuals. Cardiovascular fitness is 3. Schow RL and Nerbonne MA. 13. DiSalvo MB. Effects of directly associated with hearing Introduction to audiologic cardiovascular health on hearing sensitivity while muscular fitness is not, rehabilitation. Boston, MA: Pearson levels among musicians. 2003. however, the combination of high Allyn and Bacon; 2007. Retrieved July 12, 2010, from:

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http://etd.ohiolink.edu/view.cgi? audiological variables in adults. Arch 28. Hutchinson KM, Alessio H, and acc_num=miami1051043965. Otolaryngol 1973;97:447–51. Baiduc RR. Association between 14. Deatherage PM. Effects of music on 21. Sanden A and Axelsson A. cardiovascular health and hearing extended high frequency hearing. Comparison of cardiovascular function: Pure-tone and distortion 2003.Retrieved July 12, 2010, from: responses in noise-resistant and product otoacoustic emission http://etd.ohiolink.edu/view.cgi? noise-sensitive workers. Acta measures. Am J Audiol 2010;19:26– acc_num=miami1050962520. Otolaryngol 1981;337:75–100. 35. 15. Dagan O and Avraham K. The 22. Navarro R. Sports scan. Physician 29. Manson J, Alessio HM, Cristell M, complexity of hearing loss from a Sports Med 1990:18:16. and Hutchinson KM. Does genetics perspective. In: Van Cleve J, 23. Hutchinson KM, Alessio HM, cardiovascular health mediate ed. Genetics, disability and deafness. Spadafore M, and Adair R. Effects of hearing ability? Med Sci Sports Washington, DC: Gallaudet low-intensity exercise and noise Exercise 1994;26:866–71. University Press; 2004, 81–93. exposure on temporary threshold 30. Mitchell P, Gopinath B, McMahon 16. Ickes WM, Epsili J, and Glorig AM. shift. Scand Audiol 1991;20:121– CM, et al. Rochtchina E. Pattern A personality and noise- 27. Relationship of Type 2 diabetes to induced vasoconstriction. J Speech 24. Alessio HM and Hutchinson KM. the prevalence, incidence and Hear Res 1970;22:334–42. Cardiovascular adjustments to high- progression of age-related hearing 17. Dengerink JD, Dengerink HA, and and low-intensity exercise do not loss. Diabet Med: J Br Diabet Assoc Chermak GD. Personality and regulate temporary threshold shifts. 2009;26:483–88. vascular response as predictors of Scand Audiol 1992;21:163–72. 31. Cheng YJ, Gregg EW, Saaddine JB, et temporary threshold shifts after 25. Cristell M, Hutchinson KM, and al. Three decade change in the noise exposure. Ear Hearing Alessio HM. Effects of exercise prevalence of hearing impairment 1982;34:196–201. training on hearing ability. Scand and its association with diabetes in 18. Hutchinson K and Alessio HM. Audiol 1998;27:219–24. the United States. Prevent Med Influence of personality type on 26. Hutchinson KM, Alessio HM, 2009;49:360–64. susceptibility to the effects of noise Hoppes S. et al. Effects of 32. Bainbridge KE, Cheng YJ, Cowie exposure. J Psychol Type cardiovascular fitness and muscle CC. Potential mediators of diabetes- 1996;39:30–36. strength on hearing sensitivity. J related hearing impairment in the 19. Saxon SA and Dahle AJ. Auditory Strength Condit Res 2000;14:302–9. U.S. population: National Health threshold variations during periods 27. Alessio HM, Hutchinson KM, Price and Nutrition Examination Survey of induced high and low heart rates. AL, et al. Study finds higher 1999-2004. Diabet Care Psychophysiol 1971;81:23–9. cardiovascular fitness associated 2010;33:811–16. 20. Ismail AM, Corrigan DL, MacLeod with greater hearing acuity. Hear J DF, et al. Biophysiological and 2002;55:32–40.

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Helmholtz Resonators: They Are Everywhere!

By Scott Lake, westone Laboratories

About the Author

Scott Lake is employed by Westone Laboratories, Inc. as an engineer. He was previously employed for 20+ years in the automotive industry as an acoustics engineer, where he concentrated on full-vehicle, sub-system, and component sound quality. He is also a hobbyist composer, guitarist, and keyboardist. He can be reached at Westone Laboratories by e-mail at: [email protected].

t is a beautiful warm day, and you are I happened across Marshall Chasin’s soda bottle. Who hasn’t delighted in Idriving down the road. The nice article, “What Your Mother Never blowing across the top of an empty weather stirs your desire for some fresh Taught You about Earmold Acoustic soda bottle to hear what kind of tone air, and you move to roll down the Formulae,” in Hearing Review. As I read results? If you are like me, you’ve window down. Rather than rolling the first formula in the article for annoyed friends and family alike with down your driver side front window, Helmholtz resonance as it pertains to this simple joy. Let’s analyze the soda you inadvertently roll down a rear venting a hearing aid, I realized that this bottle in relation to its critical window. Your ears and chest are formula was relatively unchanged from Helmholtz resonator elements. Critical assaulted by that annoying and familiar the formulas I studied in my past career elements are shown in Figure 1. “whup, whup, whup,” and instantly, as an acoustician in the automotive you correct your mistake. What you industry. A Helmholtz resonance have just experienced is the sensation basically boils down to an acoustic of being inside of a Helmholtz analogy of what happens when you put resonator. It’s the same kind of a mass on a spring, hold onto the resonance you studied in school – just spring, then pull down on the mass and on a grander scale geometrically. let it go. It oscillates at a specific frequency. This article will introduce you to some basic examples of Helmholtz resonance You might be saying to yourself: “But, in areas of life other than audiology, yet there’s no mass involved with air. And, deal with the same equations and the where’s the spring?” Both mystery same physics. In my past career in the objects are alive and well in Helmholtz automotive industry, I worked on resonators, even though they are not vehicle acoustics and sound quality, visible to the naked eye. specializing in those topics during my graduate degree studies. It is HELMHOLTZ RESONATORS Figure 1. Soda bottle cross-section encouraging to me that the same Perhaps the most familiar Helmholtz physics equations and characteristics resonator with which nearly everyone There are three critical elements of any apply to the acoustics of the ear as well. has interacted is a partially full or empty simple mechanical resonating system: a

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mass, a spring, and something to set the part of the bottle 3.9 × 10−4 m2. The equation also needs mass into motion. L = Length of the neck of the bottle the volume of the bottle, which I calculate to be 1.1 × 10−3 m3. The In the case of the soda bottle, the mass This formula will calculate the length of the neck was already is the air contained in the neck of the frequency in Hz, with which we are all measured, but converted to meters, it is bottle and the spring is the air trapped familiar. Right off the bat (or in .032 m. Using this data, the equation inside the rest of the bottle. More Canadian, right off the hockey stick), it indicates that my 1L bottle should have specifically, the spring is the mechanical can be seen that the empty soda bottle an empty resonance of about 187 Hz. property of what is called the “bulk (large volume) has a lower Helmholtz modulus” of the air in the bottle. The resonant frequency than a fuller bottle Using spectral analysis software force that sets the air in the bottle’s neck (smaller volume). This agrees nicely (Audacity or Adobe Audition have this into motion is the vacuum created by with our intuition. capability), I recorded the tone and blowing across the top of the bottle. measured the frequency as 138 Hz. So, (Remember the Bernoulli principle My opinion is that it’s always better to where did the error occur? There are from speech acoustics?) The action of undergo a bit of experimentation than several places where error was perhaps blowing makes the air in the neck want to simply trust equations. Locate an introduced. First, I used 340 m/s for to escape, but the elasticity of the air in empty soda bottle – I suggest a one liter the speed of sound in air. Here in the rest of the bottle basically says to bottle (or litre – sorry, I forgot for a Colorado Springs, where I made my the air in the neck, “Get back here! moment this is a Canadian recording, the elevation is 2,073 You’ll have to come back inside!” Then publication!), because it’s rather easy to meters. This has an effect on the air it pulls on that mass of air in the bottle imagine where the neck is versus the density and ultimately affects the speed neck back toward the bottle’s interior. large volume of the bottle. Some of sound in the air. Using a calculator I Once the air in the neck goes past its readers may be disappointed to read found on a NASA website, at 2,073 m initial starting position before the that it is harder to discern where the elevation, the speed of sound blowing started, it begins pushing dividing line is between neck and larger approximates 332 m/s rather than 340. against the spring property of the volume on beer and wine bottles. So there’s one overestimation. But, it trapped air and starts to get forced back hardly accounts for the large error. the other way – towards the exit – I personally am using an empty 1L where the process repeats itself. It sparkling water bottle for my What else could have gone wrong? oscillates. As a result, the oscillating calculations. This bottle isn’t a perfect There are several remaining factors. mass disturbs the exterior air near the example; it has the funny shaped First, my measurements of everything top of the bottle at the oscillating bottom like a 2L bottle, and there’s a 5 besides the cross-sectional area of the frequency and that pleasant sounding cm length of bottle where the transition neck were crude. I could have tone is heard as those disturbances occurs from the neck portion to the overestimated the volume of the body travel acoustically to your ear. body of the bottle. After taking some of the bottle, and my length calculation rough measurements of the neck and for the neck of the bottle could be off As is the case in most areas of body of the bottle, I have recorded the as well. As it turns out, both of these audiology, equations accompany this following data: measurements are probably culprits. behaviour to calculate the natural What was not shown in the basic frequency of a basic Helmholtz • The diameter of the neck is 2.2 cm Helmholtz equation were “fudge resonator: • The length of the neck is 3.2 cm factors” that are used for what we • The height of the body section of acousticians call “end effects.” frequency = (v/2pi)*(A/V*L)^0.5 the bottle up to the transition portion is roughly 18 cm End effects account for the difficulty where: • The circumference of the bottle is that the “mass” of air in the neck has v = the speed of sound in air approximately 26 cm. moving back and forth. The air inside A = cross sectional area of the interior and outside of the bottle is actually part of the neck of the bottle Our equation asked us for the neck of a continuum of air. Some of that air V = the volume of the air in the main area, which calculates to be about is moving in concert, but other air in

32 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | the vicinity does not really want to space – what we would call an 10 Hz at most. The “whup, whup, move. There is therefore an amount of “unbaffled” end condition. The air whup” sound is audible because what surface tension between the air and the moving in and out of the neck also has you really hear is the shearing of the air inside and outside of the bottle. to convince the air that’s immediately back and forth in the open window Because this air is perfectly happy near the neck of the bottle on the frame. This phenomena can also occur sitting right next to the bottle neck on outside to bend and move. That air, with some sunroofs when fully opened. the outside, and on the inside, it pulls however, doesn’t want to go anywhere. Another potential reason for hearing on the air in the neck when that air So, there’s a fairly large resistance to the the individual events (though “slug” wants to move. Another way to air moving. This can be generalized to unconfirmed) results from your hearing think about it is that the slug of air add effective length to the neck by a system’s natural compression function seems heavier than it actually is. factor of 0.85 × the radius of the neck. of the muscle on the oval window with Newton’s first law is force = mass × On the inside of the bottle, there’s a the large pressure excursions acceleration. The additional force of the smoother transition; represented more happening in the cabin of the car. air nearby the neck pulling on the air by a baffled condition. There is still in the neck makes the mass appear resistance to move, but the generalized Why does this effect only happen with heavier than it is. effective length addition in the baffled these particular vehicle openings and condition is 0.6 × radius of the neck. not the front windows? This relates to To account for this additional force, we For this bottle, we need to add these the forcing function involved. With the can turn to the Helmholtz resonator two corrections to the length. Where open sunroof or open rear window and look at both ends of the neck to see we first had a length of 0.032 m, we can conditions, the leading edge of the what the surrounding environment add 1.45 × radius of the neck. In our open space is perpendicular to the looks like. Figure 2 shows a generic case, the effective length of the neck is direction of airflow. It’s thus very easy Helmholtz resonator and two now 0.048 m, rather than the original for an air vortex to form along that generalized end conditions. An open- 0.032 m. We thus added 50% extra leading edge. The vortex causes a local ended condition is called “unbaffled,” length to the neck. If we plug that pressure drop, which the air in the but if the neck terminates in a wall or corrected length into our equation open window frame moves to fill. But similar surface, it is called “baffled.” above, we get a resonant frequency of then the bulk modulus of the air in the This is similar to the “open” and the bottle at around 146 Hz, which is cabin (that’s the “spring” effect of the air “closed” conditions with ¼ and ½ much closer to the measured value of in the car) says, “Get back in here!” and wavelength resonators. Both hearing 136 Hz. We likely underestimated the pulls that mass of air back toward the aids and the vocal tract have volume of the bottle as well, which interior. Of course, that air can only go wavelength and Helmholtz resonators. would slightly overestimate the so far before it’s pushing on that very resonant frequency. This is actually same trapped air. Just like the mass on quite similar to how the eardrum the spring, it oscillates back and forth. (which is quite compliant) adds several All the while, vortices of air are making mm of acoustic length to the ear canal. sure that the whole thing keeps going In other words, the acoustic or effective and going. With the front windows, the length of the ear canal is about 31 or 32 leading edge is not perpendicular, and mm, even though its physical length is the vortex that provides the tweaking of only about 28 mm. the mass on the spring cannot be formed easily. Thus, the vortex is not HELMHOLTZ RESONATORS AND perpendicular to the airflow, which OUR NOISY CAR breaks up the vortex. Now that you have an understanding of Figure 2. Helmholtz resonator end conditions. the resonator in thinking about a soda Besides rolling up that rear window up bottle, the same thing is happening as or closing the sunroof, what can Let’s now take a look at what an open you drive along in a car with an open possibly be done to reduce the irritating bottle looks like on both ends of the rear window. The frequency in this case noise? We can use the mass and spring neck. The top of the bottle opens into is down in the sub-sonic range, perhaps analogy to provide some guidance. If

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 33 | you take the end of the spring that’s chambers in an exhaust system muffler. frequency from passing out of the front attached to the ground and remove it These chambers are specifically of the vehicle. from the ground, the spring becomes designed to function as Helmholtz incapable of pushing or pulling on the resonators effectively cancelling Architectural Acoustics mass that is attached to it. In the particular strong frequencies in the Yet another area where Helmholtz vehicle, how could we remove the air exhaust system. Below is a cross- resonance comes into play is with the “spring” connection to the ground? A sectional diagram of a “tri-flow” muffler, design of some cinder blocks. The simple resolution is to just slightly open which has an end of the muffler typical cinder block we’ve all seen and a front window, causing the trapped air dedicated specifically to a Helmholtz employed for various non-construction inside the body of the vehicle to no resonance (Figure 3). purposes has two chambers that are not longer be trapped. Depending on the visible in a finished wall. These cavities, strength of the resonance, it may take however, can be used as the body of a only a small 2 cm opening, but perhaps Helmholtz resonator if given an a bit more. You can also change the opening to the room where sound speed of the vehicle – by slowing down. needs to be controlled. This type of But don’t slow down too much or design has been in place for many people will start looking for retirement years; for example, perhaps you have community stickers on your vehicle’s seen it employed in some school window or bumper! gymnasium or cafeteria walls where you see open vertical “slots” in the With sunroofs, most that are factory cinder-block wall. More recently, the installed employ some kind of spring Proudfoot Company has employed loaded air deflector that pops up when Figure 3. Cross-sectional diagram of a “tri-flow” several interesting acoustic design muffler. the sunroof is opened, which forces the principles into the humble cinder vortex shedding to re-attach to the In this case, the presence of the block. Their blocks feature Helmholtz main part of the vehicle behind the Helmholtz resonator provides an resonance for low-frequency control in open sunroof location. This prevents impedance mismatch to the exhaust a room, angled surfaces on the exterior the vortex from actually setting the sound waves at the tuned frequency of of the block to serve a diffraction resonance into motion. In this case, you the resonator. At that frequency, the function, and absorbent material inside can sometimes cause the “whup, whup, sound waves are reflected back toward the block’s cavity to provide some whup” to occur by simply pulling the engine, rather than passing through damping of the resonance peak and to down on that air deflector at cruising the muffler and out the tailpipe. provide some high frequency sound speeds of perhaps 40–60 km/h. absorption. Below is a photo of the Intake System Tuner Soundcell cinder block product from WHEN HELMHOLTZ On the intake of the vehicle, there is the Proudfoot Company laying on its RESONATORS ARE USED TO also usually some kind of a “muffler” side (Figure 4). REMOVE SOUND OUTPUT system, but it is not referred to in that Keeping with the automotive way, and these days it’s usually made The port for the resonator in this case terminology, we are going to “shift from plastic. At large throttle openings, is the slot, which is easiest to see in the gears” here and talk about some a considerable amount of the sound upper left corner of the block. The practical applications of Helmholtz heard emanating from a vehicle is blocks have to be laid in a specific resonators where they are used to actually radiating out of the intake pattern so that this slot is not remove or cancel irritating sounds. system – a sort of “out through the in obstructed. The fibrous absorptive door” situation. Besides providing air material can provide both a damping of EXHAUST SYSTEM MUFFLER filtration, the intake system often has a the Helmholtz resonance frequency A relatively familiar example of how a Helmholtz resonator in a branch response; thus broadening the Helmholz resonator can be used to configuration off of the main air duct. resonance across a wider frequency remove sound are some of the This helps prevent sound of a certain range and directly absorb higher

34 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION |

banjos did not make the styles of acoustic guitars and different list. (This is nothing sizes of port holes account for some of against banjos; they just the different sounds of different types don’t have the Helmholtz of guitars, including other factors such “cool” factor.) Banjos as the choice of wood, strings, and use a drum-head as myriad other factors that acoustic guitar the primary resonating aficionados will debate ad infinitum. device, whereas these Indeed, the acoustic guitar does not other instruments use have a dominant frequency because the both resonating body actual thin layered top, and to some panels and the Helmholtz extent the back and sides of the guitar, resonator to radiate also have specific vibration modes that sound. Of course, these radiate sound and higher acoustic instruments, like our cavity modes that contribute to the Figure 4. Soundcell cinder block product from vocal chords also have ½ wavelength frequency signature. There’s an the Proudfoot Company laying on its side. resonators (strings held tightly at excellent scholarly treatment of this Image courtesy of the Proudfoot Company both ends), which results in integer topic in Chapter 9 of The Physics of (http://theproudfootcompany.com/) multiple harmonics of the fundamental Musical Instruments by Fletcher and frequency sound. The angled surfaces frequency. For our purposes, we’ll look Rossing. In the immediate vicinity of formed by the slot/neck provide an specifically at acoustic guitars and the soundhole, the radiated sound is acoustically diffracting surface for orchestral stringed instruments. dominated by the Helmholtz resonance higher frequency waves. frequency. This is the reason it’s Acoustic Guitar generally recommended to avoid WHEN HELMHOLTZ Of the list of stringed instruments using placing a microphone directly in front RESONATORS ARE USED TO Helmholtz resonance, it’s probably safe of the soundhole when amplifying or ENHANCE SOUND OUTPUT to say that the flattop acoustic guitar is recording acoustic guitar. Acoustic Now that we’ve covered some territory the most well-known. Even if you aren’t guitar design and construction where Helmholtz resonators are used to currently a guitar player, you have technology changes rather slowly reduce irritating frequencies, we’ll shift probably tried strumming an acoustic because tradition tends to dominate gears again and discuss when guitar at some point in your life. If designs. Some relatively recent trends, Helmholtz resonators are used to you’ve looked into the hole of an however, promise to keep the debates enhance acoustic output. Aside from acoustic guitar, you know that the alive and well for many years to come. hearing aid acoustic tuning, we find “neck” doesn’t really seem to exist – it’s Some of these recent trends involve these examples mostly in the musical just a hole in the thin top of the guitar. changing the shape of the soundhole to instrument world. Recall that the end correction factors move it away from the traditionally introduced some additional length and recognized central location. Tacoma Acoustic Stringed Instruments that they were related to the radius of Guitar Company, for example, has Any acoustic stringed instrument that the neck. In this case, the radius of the made this design a feature of most of has a body and a port to the exterior of “neck” is many times larger than the their acoustic guitars and mandolins. the instrument has Helmholtz length of the neck. The end correction (www.tacomaguitars.com/products). resonance as part of its acoustic factors thus dominate the actual length Another trend seen for some years in signature. Instruments that likely come of the neck. The end conditions can be boutique acoustic guitar manufacturers to mind immediately are acoustic considered to be a baffled condition on is to put an additional, yet typically guitars, orchestral stringed instruments both ends of the neck. The frequency smaller hole in the side of the guitar. (those f-holes on the top of the at which this Helmholtz resonator Some guitar builders that have adopted instruments constitute for the port), radiates sound dominates the low this trend are McKnight Guitars mandolins, bouzoukis, certain lutes frequency character of the sound of (http://www.mcknightguitars.com/soun and zithers, autoharps, etc. Note that acoustic guitars. Several different body dports.html) and Charles Fox Guitars

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 35 |

few cool design elements that allow it to have several different “voices.” Pertinent to our discussion is the side port that many cajons use to provide a Helmholtz resonance. This allows the box to resonate with a low and rich tone when the player wants a bass or kick drum type sound. Other design factors include a loose side to “slap” or strings mounted on the interior of the cajon to provide a more “snare” like sound. LP Percussion has a new take on the cajon side port, with a sliding cover Figure 5. Acoustic guitar with the O-Port superimposed. Image courtesy of Dare Music Group. for the port hole, which allows an adjustable Helmholtz resonance (http://www.charlesfoxguitars.com/intr Helmholtz resonance includes the frequency. This sliding port cover is o_design.html). violin, viola, cello, and contrabass. available on their Kevin Ricard model. With these instruments, the ports are This instrument can be seen at O-Port Modification commonly known as “f-holes,” due to http://www.lpmusic.com/Product_Sho A new product on the market that their shape resembling a lower-case wcase/Whats_New/kevin-ricard- specifically aims to change the letter “f.” These holes have been shown cajon.html. Helmholtz resonance of an acoustic in scholarly articles to provide more guitar is the O-Port from Dare Music than just the port for Helmholtz Djembe (percussion instrument) Group (http://www.dmg-austin.com). resonance, because they also The djembe uses Helmholtz resonance Whereas the typical acoustic guitar has significantly change the stiffness of the in yet another unique way. Djembe a relatively shallow hole “neck,” the O- top of the instrument. Whereas construction is somewhat typical of Port aims to increase the length and acoustic guitars with wood tops use a end conditions of the acoustic guitar bracing pattern to provide the neck directly. Below is a photo of the necessary stiffness to withstand the side of an acoustic guitar with the O- tension of the strings, the stiffness of Port superimposed as if the side of the the top of a violin is provided by the guitar was translucent and one could curvature of the top itself. This is also view the O-Port internally mounted in true for archtop acoustic guitars (which the port of the guitar. also employ f-hole type ports). So the placement, size, and shape of the f- With the O-Port, the flared design of holes affect more than just the the port reminds one of similar efforts Helmholtz resonance of the instrument. in bass-reflex speaker design. Bass Nevertheless, efforts to control the reflex is the phenomenon where a thickness of the top at the f-hole trapped mass of air (sometimes referred locations, the size and shape of the f- to as an inertance) oscillates as a single hole, and the smoothness of the f-hole’s unit and creates a Helmholtz edges are all design factors that the resonance. The vent associated luthier takes into consideration in resonance in hearing aids is an example designing these instruments. Figure 6. A cross sectional diagram of a djembe showing the trapped volume, the drumhead, of a bass reflex system. and the port/neck. Cajon (percussion instrument) Orchestral Stringed Instruments Constructing the cajon is fairly simple. The other well-known family of Cajon is a Spanish word for “box,” and drums in general, but where this design stringed instruments employing the instrument is basically a box with a varies from a drum-kit drum, is that the

36 CANADIAN HEARING REPORT | REVUE CANADIENNE D’AUDITION | body of the djembe that narrows down at all times to take advantage of the sound, and enhance desirable sound in to a neck section. Below is a cross resonance. automotive, architectural and musical sectional diagram of a djembe showing acoustics. Hopefully the next time you the trapped volume, the drumhead, SUMMARY tune a vent in a hearing aid earpiece, and the port/neck (Figure 6). I hope you have enjoyed this romp you’ll remember your unique through the garden of Helmholtz connection to other acousticians Some djembe players will take resonance and can spot other instances applying the same principle across very advantage of the dual-tone (open port of this most useful acoustic tuning different industries. versus closed) capability of the djembe device in your day-to-day life. We’ve by holding the drum between their covered the basic physics of how these CONFLICTS knees and lifting the drum, though resonators work, and how they are None declared. most keep the drum up off of the floor employed to both reduce irritating

REVUE CANADIENNE D’AUDITION | CANADIAN HEARING REPORT 37 | audioLogY neWs Hearing News Network Noise and

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