Hearing - Hearing; Audition THE EAR Range of audibility...

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Hearing; Audition THE EAR Range of audibility ranges from 20 to 20K Hz (Note: in adults the higher freq range is decreased from childhood to 14 to 15K Hz). Our ears can detect over 1000 different pitches of sound, and over 250 different intensities (perceived as changes in loudness) http://www.wisc-online.com/objects/index_tj.asp?objID=AP1502 Short animation of Anatomy of the Ear Composed of 3 parts on an anatomical basis: Middle (tympanic membrane, ossicles) Inner (vestibular system, cochlea) SEE BELOW Composed of 2 parts on a physiological basis Outer Inner External ear A. Auricle (L for ear) or pinna (L for wing) pix from http://www.augie.edu/perry/ear/hearmech.htm Video = http://www.wisc-online.com/objects/index_tj.asp?objID=AP1502 Functions: gathers and directs sound waves through external auditory meatus to tympanic membrane Protection for tympanic membrane Helps with sound localization B. EAM
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Function: conduct sd to TM @ 25mm in length; @8mm in width Outer support of 1/3 to ½ of EAM is cartilaginous; turns into bone Axis is directed downward, thus no likely to accumulate water or foreign material. Otoscopic view—lift gently up on auricle Function, with pinna is to amplify acoustic signals, esp in speech frequencies. Outer 1/3 of lining has cilia; cerumen produced here Cerumen is noxious, bitter, sticky Repels insects and foreign substances http://www.audiologynet.com/anatomy-of-the-ear.html Lists many great websites!! EAM and auricle cause sd intensification of @ 15-16 dB at TM Middle ear http://www.innerbody.com/anim/ear.html Air-filled cavity behind the tympanic membrane In the petrous portion of ? Turns acoustic energy into mechanical TM: 3 layers; middle layer is fibrous which allows for compliance of TM Three ossicles (ossicular chain) (transmit sound energy from the tympanic membrane, turns it into mechanical, and transmit to the cochlea). Amplification occurs here, too--@ 30dB Malleus—lgest; attaches to TM Incus—between malleus and stapes Stapes—footplate rocks in oval window The posterior wall of the epitympanic recess is perforated by an opening or aditus. This aditus communicates with mastoid air cells.
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Why is this important? Bacteria can spread from the middle ear to mastoid air cells, causing mastoiditis. Important muscles of ME Are smallest muscles in human body Stapedius : attaches to posterior neck of stapes Action: when contracts, stapes is rotated posteriorly, thus stiffening ossicular chain Tensor tympani: attaches to manubrium of malleus Action: pulls malleus antero-medially and stiffens ossicular chain Both muscle actions result in a reduction in transmission of low
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This note was uploaded on 05/16/2011 for the course SPA 3101 taught by Professor Carson,d during the Spring '08 term at University of Central Florida.

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Hearing - Hearing; Audition THE EAR Range of audibility...

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