Lecture 3 Flashcards
Pure tone audiometry
Threshold of hearing across the frequency range measured in dB SPL
Air conduction
Via earphone or sound field speaker
Measures the response of the whole auditory system
Bone conduction
Via bone conductor/vibrator
Measures response of the cochlea
Any sound presented to one ear by BC will be heard by the better cochlea
Air bone gap
If the bone conduction results match the air conduction results, that is considered sensorineural hearing loss. The ear canal isn’t effecting the results at all, it’s most likely generating in the cochlea or auditory nerve
If bone conduction is better than the air conduction results (> 10 dB), then the cochlea is functioning fine and the problem is in the middle or outer ear (conductive hearing loss)
If mixed results, then there is mixed hearing loss
Threshold
The level at which subject can just hear the tone 50% of the time
Or
The lowest level at which subject responds twice or three times
Interaural attenuation
An amount by which the sound loses energy as it crosses the skull
Depends on whether the sound is introduced by supra aural phones (at least 40 dB) or inserts (at least 60 dB)
Cross over
When high enough levels or sound are presented to one ear and it exceed the IA, the signal crosses over
We can isolate the non-test ear by putting masking noise into it
Masking
Carefully controlled amount of noise with specific acoustic characteristics, introduced to the non test ear when IA has been exceeded
- just covers frequency that’s being tested
Happens for bone conduction much more often
Mask for AC when AC threshold in test ear - IA > unmasked BC threshold
Narrow band noise for pure tone, speech noise for speech tests
Right ear masked threshold
Means the right ear is being tested, left ear is being masked
Over masking or masking dilemma
In bilateral conductive hearing loss of a moderate degree or greater, it may be impossible to put enough masking into the non-test ea, without the noise itself crossing back over to the test ear
Acute otitis media
Middle ear infection, red irritated ear drum
Otitis media with effusion
There’s fluid sitting behind the ear drum
PE tube
Too much persistent fluid, to provide ventilation because Eustachian tube isn’t working properly
Tympanosclerosis
Scaring on the tympanic membrane
Exostoses
Bony growth in the ear canal
Surfers ear, more common in people who are constantly exposed to colder water
