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Sound and the Ear Chapter 2 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Chapter© Jones & Bartlett 2 Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Sound and the Ear © Jones Karen &J. Kushla,Bartlett ScD, Learning, CCC-A, FAAA LLC © Jones & Bartlett Learning, LLC Lecturer NOT School FOR of SALE Communication OR DISTRIBUTION Disorders and Deafness NOT FOR SALE OR DISTRIBUTION Kean University © Jones & Bartlett Key Learning, Terms LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR Acceleration DISTRIBUTION Incus NOT FOR SALE OR Saccule DISTRIBUTION Acoustics Inertia Scala media Auditory labyrinth Inner hair cells Scala tympani Basilar membrane Linear scale Scala vestibuli Bel Logarithmic scale Semicircular canals Boyle’s law Malleus Sensorineural hearing loss Broca’s area © Jones & Bartlett Mass Learning, LLC Simple harmonic© Jones motion (SHM) & Bartlett Learning, LLC Brownian motion Membranous labyrinth Sound Cochlea NOT FOR SALE OR Mixed DISTRIBUTION hearing loss Stapedius muscleNOT FOR SALE OR DISTRIBUTION Compression Organ of Corti Stapes Condensation Osseous labyrinth Tectorial membrane Conductive hearing loss Ossicular chain Tensor tympani muscle Decibel (dB) Ossicles Tonotopic organization © Jones Decibel & hearing Bartlett level (dB Learning, HL) LLC Outer ear © Jones Transducer & Bartlett Learning, LLC Decibel sensation level (dB SL) Outer hair cells Traveling wave theory NOT Decibel FOR sound SALE pressure OR level DISTRIBUTION (dB SPL) Oval window NOT TympanicFOR SALE membrane OR DISTRIBUTION Displacement Pars flaccida Uniform circular motion Elastic Pars tensa Utricle Endocochlear electrical potential Pascal (Pa) Vector Endolymph Perilymph Vestibular labyrinth Equilibrium Pinna Vestibular membrane © Jones & Bartlett Eustachian Learning, tube LLC Pressure wave© Jones & Bartlett Vestibule Learning, LLC NOT FOR SALE OR External DISTRIBUTION auditory meatus Propagation NOT FOR SALE OR Wavelength DISTRIBUTION Force Pure tone Wernicke’s area Helicotrema Rarefaction Impedance-matching transformer Round window © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Objectives • Describe the characteristics of sound. • Define the concept of simple harmonic motion and its relationship to periodic sounds. • Summarize the physical characteristics of sound. © Jones• Identify the anatomy of the auditory system and trace the transmission of sound throughout. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT• FOR Differentiate the types of hearing loss an abnormality in the auditory system can cause. SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Chapter opener image: © Filip Fuxa/Shutterstock © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 9781284132793_CH02_015_036.indd 15 30/06/17 10:20 am © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 16 Chapter 2 Sound and the Ear © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC IntroductionNOT FOR SALE OR DISTRIBUTIONwith the medium of transmissionNOT we FORcall air. SALE Air OR DISTRIBUTION molecules are not static; in fact, they are moving For the speech-language pathologist to work within constantly in random fashion. This random move- his or her scope of practice with individuals with ment at high speeds is called Brownian motion, hearing loss, interpret audiograms, and screen for named for Robert Brown (1773–1858), a Scottish auditory disorders, one must have a firm under- © Jones & Bartlett Learning, LLC botanist who ©described Jones this & motion,Bartlett which Learning, results LLC standing of what, how, and why we hear. The inten- from the impact of molecules found within a gas NOTtion FOR of this SALE chapter ORis to provideDISTRIBUTION an overview of the NOT FOR SALE OR DISTRIBUTION or liquid. Brownian motion causes these air mol- characteristics of sound, sound transmission, and ecules to collide with each other and with whatever the path sound takes as it is transmitted through the is in their path—walls, furniture, or people. These auditory system. molecules are elastic—that is, the objects exhibit a As a supplement to exhaustive coursework © Jones & Bartlett Learning, LLC © Jonestendency & to Bartlett resist deformity Learning, and return LLC to their rest required by the American Speech-Language- NOT FOR SALE OR DISTRIBUTION NOTposition—so FOR SALE there isOR no changeDISTRIBUTION in their shape when Hearing Association, the intention of the following they bump into each other and/or other objects. information is to provide the reader with a sum- mary of acoustics and anatomy and physiology of These collisions produce pressure. Although we the auditory system to reference within this text, may not be able to feel that pressure, it is there. You rather than to ©take Jones the place & of Bartlett that coursework. Learning,feel LLC this pressure whenever air ©is Jonesset into motion, & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONsuch as on a windy day or when NOTwe speak. FOR SALE OR DISTRIBUTION A source of energy, such as a force, is the next General Characteristics prerequisite. Force is a push or a pull on an object, of Sound and is a vector that has both magnitude (some Sound is all around us, although it may be too faint amount greater than zero) and direction. Force is © Jonesfor us to hear& Bartlett or too intense Learning, for us to listen LLC to for any mathematically© determinedJones & Bartlettto be the productLearning, of LLC NOTlength FOR of time. SALE In the OR 1700s, DISTRIBUTION the British philosopher mass times accelerationNOT FOR (F SALE= ma). ORAir moleculesDISTRIBUTION George Berkeley asked the question, “If a tree falls have mass (the quantity of matter present). Mass is in the forest and no one is around to hear it, does it not identical to weight because weight is affected by make a sound?” Of course it does—unless it falls on gravitational forces; however, for our purposes, mass another planet with little to no gaseous atmosphere, and weight are the same. Because air molecules have © Jones & Bartlettin which Learning, case there LLCis no sound. © Jonesmass, they & obeyBartlett laws of Learning, motion set forth LLC by the great NOT FOR SALE ORThe DISTRIBUTION study of sound is a branch of physics calledNOT English FOR scientist SALE Sir OR Isaac DISTRIBUTION Newton (1643–1727), the acoustics. Sound itself is a physical phenomenon first of which states that all bodies remain at rest that is described as the movement or propagation or in a state of uniform motion unless other forces of a disturbance (i.e., a vibration) through an elas- act in opposition. (This property is called inertia.) tic medium (e.g.,© airJones molecules) & Bartlett without permanent Learning, The LLC amount of inertia an object© (e.g., Jones an air & mol Bartlett- Learning, LLC ecule) has is directly proportional to its mass: The displacement ofNOT the particles. FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION There are three prerequisites for production of greater an object’s mass, the greater its inertia. An sound: (1) a source of energy (e.g., a force), (2) a vibrat- outside force must be applied to change this ten- ing object that generates an audible pressure wave, dency. Acceleration is the speed (distance traveled and (3) a medium of transmission (e.g., air). However, per unit time) of an object per unit time, which is represented mathematically as length . When a force © Jonesa receiver & of Bartlett these prerequisites Learning, of sound LLC production © Jones & Bartlett(time)2 Learning, LLC NOTis optional; FOR SALE that is, a ORlistener DISTRIBUTION is not required. is applied to theNOT air particles FOR SALE by a moving OR object, DISTRIBUTION the As human beings, we produce sound primarily in air particles will travel in the direction of the force. air, so let’s begin our discussion of the prerequisites The amount of this distance is proportional to the © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 9781284132793_CH02_015_036.indd 16 30/06/17 10:20 am © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION General Characteristics of Sound 17 © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC magnitude ofNOT the appliedFOR SALEforce—a OR large DISTRIBUTION force will Elasticity in the tuning NOTfork tine FOR allows SALE for OR DISTRIBUTION cause the object to travel much further than a small this displacement, but also generates a restor- force. Therefore, the greater the force applied to the ing force that momentarily stops the movement object, the greater the distance the object travels by at the point of maximum amplitude away from that force; in addition, the restoring force is pro- the rest position. The restoring force pushes the © Jonesportional & Bartlettto the displacement Learning, (i.e., theLLC object obeys tuning fork© tines Jones back &to Bartletttheir rest position,Learning, but LLC NOTHooke’s FOR law,SALE named OR for DISTRIBUTION Robert Hooke [1635–1703], inertia carriesNOT the FORtines pastSALE the
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