lecture 16: hearing aids - exam 3 Flashcards
what is a hearing aid
primary treatment for hearing loss
15% of US pop. >65 wears a hearing aid
only 20% of listeners who would benefit from a hearing aid actually use one
personal sound amplification products
no FDA prove
very similar to hearing aid
make sounds, particularly speech, audible
assistive listening devices
often used in conjunction w/ hearing aids but not always
tech used to improve speech audibility
microphone & headphone system
hearing assistive technology
ALDs & other technology that helps hard of hearing people function easier
flashing lights for telephones & doorbells
caption phones
behind the ear HA
2 mics
program button –> switch to car, phone, music, etc
volume control
battery door, on/off
ear hook (outside of hear)
tubing (goes into ear) connects to same area
receiver –> speaker
BTE advantages
powerful amplification
durable
appropriate for children –> can connect to teacher microphone
roomed for features
longest battery life
BTE disadvantages
visibility/large size
requires ear mold & tubing –> needs to be replaced often & can only be done by AuD
limited bandwidth –> tube has a long way to travel, may block impedance
open-fit
essentially same as BTE HA, but coupled w/ a dome/slim tube instead of ear mold
amplifies high freqs while allowing low freqs to be heard naturally
sloping SNHL
open-fit advantages
no occlusion effect (hearing voice in your head)
cosmetic appeal
no ear mold required
open-fit disadvantages
only appropriate for mild to moderate high freq losses
receiver in the canal (RIC)
most popular
same as BTE & open fit but receiver is in the ear canal
sound presented directly into ear canal rather than through a tube
dome tip or earmold
RIC advantages
smaller
same advantages as open fit
theoretically larger bandwidth - receiver in ear
RIC disadvantages
more prone to damage from wax/moisture in the ear canal
in the ear
mics
program button
volume control wheel
pressure vent –> relieve / equalize to ambient pressure
battery door
receiver –> down in ear canal
ITE advantages
may be less visible than BTE
may have room for features
easier to put in / take out –> BTE takes a lot of practice, more parts
ITE disadvantages
less powerful than BTE
shorter battery life than BTE
prone to cerumen problems
dexterity required to manipulate controls
in the canal & completely in canal
tinier & tinier, farther & farther in the ear canal
1 mic –> can’t pick out sound from the front & reduce from the back but get more pinna localization
battery door
receiver –> down in ear canal
no volume wheel, program button, or 2nd mic
ITC & CIC advantages
least visible
ITC &CIC disadvantages
typically not powerful
no room for volume / other features
difficult to put in & take out
shortest battery life
lyric
leave it in full time & replace when battery dies every 6 months
bone anchored BAHA
one piece surgically screwed into head behind ear
other piece screws on
works like bone knocker, bypasses middle ear
ear lens
transduces into laser signal & flashes @ photo receptors in inner ear
HA processing
continuous wave in air
enters mic, moves mesh, creates electrocurrent using ADC
ADC samples & quantizes
processed in computer & amplified (2 mics into 1 sound), back into continuous signal
sent through speaker & into ear
HA processing w/ non flat HL
don’t want to amplify all freqs equally
putting signal in freq domain allows you to filter different freq regions
then you can selectively manipulate diff freq regions
HAs efficiently provide gain from 250-6000 Hz
