A Case Study on the Effectiveness of Acoustic Shields in Live Ensemble Rehearsals
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LIBERA, REBECCA CHRISTINE HAMMONTREE, D. M. A. Shielding a Musician: A Case Study on the Effectiveness of Acoustic Shields in Live Ensemble Rehearsals. (2009) Directed by Dr. Michael Burns and Dr. Sandra Mace. 101 pp. The purpose of this study was to determine the effectiveness of acoustic shields at reducing sound levels experienced by a bassoonist during rehearsals of two professional orchestras. The primary research question was as follows: Do acoustic shields reduce sound levels experienced by a bassoonist to 85 dBA or below? A preliminary research question was: without an acoustic shield, do bassoonists in professional orchestras experience sound levels that exceed 85 dBA? The 85 dBA limit has been derived from the NIOSH recommended limits of sound-level exposure. Sound levels of a professional bassoonist were measured across sixteen rehearsals during the 2007-2008 concert season. The bassoonist wore Cirrus Research CR: 100B doseBadge sound dosimeters on each shoulder. One of two commercially available acoustic shields was placed behind the bassoonist; shields used were manufactured by Manhasset and Wenger. The results indicated that bassoonists in professional orchestras experienced average sound levels that exceed 85 dBA, and the use of acoustic shields did not reduce average sound levels to 85 dBA. SHIELDING A MUSICIAN: A CASE STUDY ON THE EFFECTIVENESS OF ACOUSTIC SHIELDS IN LIVE ENSEMBLE REHEARSALS by Rebecca Christine Hammontree Libera A Dissertation Submitted to the Faculty of the Graduate School at The University of North Carolina at Greensboro in Partial Fulfillment of the Requirements for the Degree Doctor of Musical Arts Greensboro 2009 Approved by Michael Burns Committee Co-Chair Sandra Mace Committee Co-Chair © 2009 Rebecca Christine Hammontree Libera APPROVAL PAGE This dissertation has been approved by the following committee of the Faculty of the Graduate School at The University of North Carolina at Greensboro. Committee Co-Chair ____________________________________ Michael Burns Committee Co-Chair ____________________________________ Sandra Mace Committee Members ____________________________________ Mary Ashley Barret ____________________________________ Kelly Burke April 7, 2009 Date of Acceptance by Committee March 23, 2009 Date of Final Oral Examination ii ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Michael Burns, for his patient guidance through the preparation of this document and this degree program. Special thanks are also owed to Dr. Sandra Mace for her knowledge and patience. They, along with Dr. Kelly Burke, Dr. Mary Ashley Barret, and my other professors have provided me countless opportunities for growth and learning throughout my time in North Carolina. I would also like to thank Dr. Donald Hodges, and the other faculty members of the Music Research Institute (MRi). Without their support and equipment, this dissertation would not have been possible. The Graduate School at The University of North Carolina at Greensboro has also contributed greatly to this dissertation. The assistance I received through two summer research assistantships allowed me to prepare my data, write an article, and write drafts of this document. Sincere thanks are also owed to John Gordon Ross, Dr. David Hagy, my fellow bassoonists, and all the members of the Western Piedmont Symphony and Salisbury Symphony. Thank you for allowing me to intrude upon rehearsals with my equipment. Your patience is appreciated. Thanks to all of my family for listening when I ramble, and for reading drafts I sent you. Thank you Matt for supporting me, encouraging me, and for making dinner. Thanks to my parents, Mary and Larry, and my siblings for helping me get this far in my education. Finally, thank you to all my teachers along the way. You have helped me become a better musician, teacher, writer, and human being. iii TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii CHAPTER I. INTRODUCTION .................................................................................................1 Importance of Hearing .................................................................................1 Anatomy of the Ear ......................................................................................5 Process of Hearing .......................................................................................7 Types of Hearing Loss .................................................................................9 Legislation and Standards ..........................................................................11 Aim of the Present Study ...........................................................................15 II. SURVEY OF LITERATURE ..............................................................................17 Acoustic Shield Studies .............................................................................18 Orchestra Studies .......................................................................................19 Acoustic Music Studies..............................................................................25 Remaining Studies .....................................................................................28 Summary of the Literature .........................................................................29 III. PROCEDURES ...................................................................................................30 Selection of Subject and Venues................................................................31 Acoustic Shields Tested .............................................................................32 Data Collection Methodology ....................................................................34 Data Collection and Measurement Period .................................................36 IV. RESULTS ............................................................................................................37 Preliminary Research Question..................................................................37 Primary Research Question........................................................................39 iv V. DISCUSSION, SUMMARY, AND CONCLUSIONS ........................................42 Differences and Sound Sources .................................................................42 Influence of Time .......................................................................................47 Alternate Methods of Hearing Protection ..................................................51 Summary ....................................................................................................58 Limitations of the Study.............................................................................59 Recommendations for Future Research .....................................................59 REFERENCES ..................................................................................................................61 APPENDIX A. ADDITIONAL STUDIES.......................................................................75 APPENDIX B. METHOD OF PERCENT DOSE CALCULATION ..............................81 APPENDIX C. DATA ......................................................................................................83 APPENDIX D. OCCUPATIONAL HEARING CONSERVATIONIST CERTIFICATION ................................................................................86 APPENDIX E. SAMPLE REHEARSAL DATA FORM.................................................88 APPENDIX F. CALL SHEETS FOR REHEARSALS ....................................................90 APPENDIX G. PERMISSION TO USE MATERIALS ..................................................98 v LIST OF TABLES Page Table 1. Exchange Rates of NIOSH and OSHA Standards ...........................................13 Table 2. Acoustic Shield Studies ...................................................................................18 Table 3. Orchestra Studies .............................................................................................20 Table 4. Acoustic Music Studies....................................................................................26 Table 5. Typical Day of the Bassoonist .........................................................................31 Table 6. Description of Shields ......................................................................................33 Table 7. Hypothetical Day 1 of the Bassoonist Without a Shield..................................48 Table 8. Hypothetical Day 1 of the Bassoonist With a Shield .......................................49 Table 9. Hypothetical Day 2 of the Bassoonist Without a Shield..................................49 Table 10. Hypothetical Day 2 of the Bassoonist With a Shield .......................................49 Table 11. Hypothetical Day 3 of the Bassoonist Without a Shield..................................50 Table 12. Hypothetical Day 3 of the Bassoonist With a Shield .......................................50 vi LIST OF FIGURES Page Figure 1. Frequency of Specific Vowels and Consonants .................................................2 Figure 2. Piano Frequencies ..............................................................................................3 Figure 3. Overtone Series on F and C ...............................................................................4