6/1000 born with hearing loss

Biggest age group is 75+

Middle ear infections

Can cause delayed language and social development if aquired at critical learnign period

Behavioral: The patient has to do something

     i.e. do I hear it or do I not hear it?

Physiological:Present a sound but the resonance is correlated with some type of behavioral measures

    i.e. pure tones, tuning forks

Detection: presenting some stimulus, then detecting speech or pure tone

      I.e. is that stimulus present or absent (threshold)

Discrimination: The ability to discriminate between two sounds, whether something is same or different

    i.e. "ba pa" vs. "ba ba"

Recognition: The ability to recognize and repeat whatever stimulus you just heard

Outer Ear

-Anatomy

-Functions

Anatomy:

-Extrernal auditory meadis (creates ear wax)

-External Auditory Canal (bone, in the skull, terminates at ear drum)

Primary functions: funneled amplify and shape incoming sounds passively.  Protect structures inside. Localization

Middle ear

-Anatomy

-Function

Anatomy:

-Eardrum (air filled cavity)

-Osscicular chain: Malleus, incus, stapes (mechanical lever)

Function:

-Helps with impedance mismatch between air and fluid

-2 muscles for protection

-Estatchian tube (equalize pressure btwn atmosphere and cavity)

-Stimulate oval window to send acoustic signals through fluid  filled cavity to set up traveling wave

Inner Ear

-Anatomy

-Function

Anatomy:

-Semi Circular canals (vestibular system)

-cochlea (sensory portion of auditory system)

-Outer/Inner hair cells

-8th cranial nerve = auditory/ vestibular nerve

-Nerve fibers

Functions:

-Transduce mechanical vibrations to hydraulic to nerve impulses

-Tonotopically organized 

-Band pass filters: lets some frequencies through and others no

when ear produces sound independently 

(backwards sound transduction)

Air conduction (AC)

-Ear infections

-Esachian tube disfunction

-Skin tissue growth

-Too narrow of air canal

-Stiffening of ossciles

-Fluid in middle ear

-Disordered coding of information (i.e. sound level will be different than someone with CHL or NHL

-SNHL have abnormal spontaneous activity (when AN fires without stimulus) 

-Abnormal tuning of the tonotopic organization, because less selective (decrease in how selective auditory apartis is) which makes fuzzy signal

-Abnormal latencies 

-Abnormal nueral adaptation

Hearing loss by bone conduction, and a greater degree of hearing loss when measured by air conduction (AC>BC)

-Normal: P & T stop hearing at same time

-Diminished: P stops hearing tone before T, suggests a SNHL

-Prolonged: P hears tone longer than tester, May suggest a conductive hearing impairment

-Results of patient is compared with results of practioner

-The tuning fork is set into vibration and placed on the mastoid bone right behind the oracil, and is kept there by the tester until the patient can no longer here the tone and then the tester times how much longer they can hear the tone for

-This assumes that the tester has normal hearing, or at least better hearing than patient

-Assume that patient has sufficent hearing sensitivity to even hear the tone from the beginning

Positive: P reports tone is louder when tone is via air canal (suggests normal hearing, but may suggest SNHL)

Negative: P reports tone is louder by bone conduction pathway (mastoid bone), associated/ suggests with CHL

P asked which is louder, when tuning fork is placed on mastoid or next to air canal

-Compares hearing sensitivity with AC to that with BC

Positive: When ear canal open and closed will occilate and go from soft to loud, pulsating sound (normal hearing sensitivity or SNHL) 

Negative: no change in loudness when Open and closed (CHL) 

-Tuning fork put on midline of patient's skull

-Patient asked where they hear the sound loudest

-Stenger principle (if two tones are identical, when bone-conduction sensitivy is poorer in one ear than in the other the tone will be perceived as softer in poorer ear)

Midline Sensation: Suggest normal hearing or equal amount of hearing loss in each ear

Unilateral SNHL: will hear tone in the better ear, and the poorer ear will have SNHL

Unilateral CHL: will hear tone in poorer ear, that ear has the hearing loss

1) medium

2) Force (for movement of air molecules)

3) Elasticity (need air molecules to recover form destruciton)

The amount of cycles per second

F=1/T

Amount of time required for one cycle

T=1/F

VoWels --> lower frequencies

Consonants --> higher frequencies

Longer wavelengths of vowels move more easier around corners and obstructions than shorter wavelengths of consonants. Somone of hearing impairment can therefore hear vowels in a loud room than consonants.

a linear measure of distance that sound travels

Wavelength = c/f

out-of-phase if two sinusoids of the same freq start in different phases

When sine waves are 180 degrees out of phase, when they are summed together they cancel eachother out

-Associated with amplitude

-The higher the amplitude the higher the intensity

-Can be measured in dB

-dB: a unit that is demensionless because its defind by a log ratio

Force per unit area in Pascals (Pa)

Smallest pressure required to for a just audible sound is 20microPa

Damaging sounds can be 2x10^8 microPa

unit is joule (J)--> 10 million ergs

Work is done whenever a certain amount of work is done as energy is expended

when the frequency is doubled (it is raised one octave) 

i.e. 200, 400, 800