Lecture 2.1 Flashcards
What are the components of all hearing aids?
microphone - picks up the sound
amplifier - increases the gain
battery - power source
signal processor - computer within the aid
receiver - sends amplified sound to the ear
What is the best way to treat most hearing loss?
amplification
How do hearing aids work?
sound picked up by microphones
sent to amplifier and then signal processor
amplified signal transferred to receiver to be delivered to ear
What are some factors that contribute to candidacy for hearing aids?
age
type and degree of hearing loss
monoaural vs. binaural
needs and lifestyle
technology level
dexterity
physical and or psychological factors
What is binaural squelch/squelch effect?
aka cocktail party effect
a signal in the presence of noise is more easily detected when the signal and noise are presented to both ears rather than one ear alone
- benefit of adding the ear with the poorer signal to noise ratio
binaural listener can attend to a conversation in the presence of background noise
What is the head shadow effect?
attenuation of sound that occurs as it passes through the head
when hearing on side of poor ear it reduces the loudness of sound as it passes through the head to reach the better ear
What is the localization effect?
the ability to know the direction of the sound and to orientate in an environment
What is the summation effect?
a boost in perceived loudness when both ears hear a signal
Are 2 hearing aids always better than one?
yes unless only single sided deficits
Who uses BTE hearing aids?
all ages, mild to profound degree of hearing loss
What are the types of BTE hearing aids?
open fit
receiver in the canal
What are open fit hearing aids?
thin tube is attached to the device and a dome is used along with it, allows ear canal to remain open
suitable for individuals with excessive wax build up
What are receiver-in-the-canal hearing aids?
has an external receiver which goes into the ear canal
for mild-severe hearing loss
no “plugged up” feeling
minimizes amplification of own voice by allowing sounds to escape through ear canal
What are the types of custom hearing aids?
in the ear (ITE)
in the canal (ITC)
completely in the canal (CIC)
all made using ear mold impression of the patient’s ear
What is an in-the-ear hearing aid?
molded and fits the outer ear
suitable for mild-severe hearing loss
not recommended for children because the casing would need to be replaced often as the child’s ear keeps growing
What is an in-the-canal hearing aid?
molded and fits partly in the ear canal
for mild to moderately severe hearing loss
not suitable for children, individuals with severe to profound hearing loss, or individuals with poor dexterity (harder to insert and remove device)
What is a completely in the ear hearing aid?
molded to fit full inside the ear canal
smallest type, nearly invisible
not recommended for children or individuals with severe-profound hearing loss
What is the hearing aid fitting process?
assessment of hearing loss
selection of hearing aid
verification of hearing aid
outcome validation
Why is hearing aid fitting important?
hearing aids fit comfortably
output of hearing aid meets specific hearing needs and lifestyle needs
speech is audible and comfortable across a broad range of frequencies
What occurs during a hearing assessment?
case history
- medical, hearing, family, noise exposure, etc.
otoscopy
audiologic assessment
- acoustic immittance procedures (ex. tympanometry)
- OAEs
- pure-tone audiometry (air and bone conduction)
- ABR
What is acoustic immittance?
measure of air pressure flow
useful in assessing anatomy of the middle ear and then function of the tympanic membrane and muscle reflexes
What do OAEs measure?
the responses from hair cells in the inner ear
What is pure tone audiometry?
behavioural test that measures hearing thresholds through air and bone conduction
using in hearing aid programming when available
What is ABR?
auditory brainstem response
records evoked potentials from auditory nerve and brainstem structures
What are the physical features to be considered during selection of hearing aids?
style of hearing aids (depends on type and degree of loss, age, appearance, etc.)
binaural vs. monaural
ear mold/shell type and configuration
number and size of user controls
compatibility with other technologies
What are some electroacoustic characteristics to be considered during hearing aid selections?
microphones
noise reduction
binaural processing
program options
also:
digital feedback control
frequency lowering
telecoil sensitivity
What is the role of microphones in hearing aids?
pick up sound and send it to processor
have at least one, usually 2 or more
hearing aids that communicate between ears use microphones on both aids to collect sound from specific locations
What are the types of microphones used in hearing aids?
omni-directional - picks up sound from all around
directional - multiple microphones work to reduce sound from behind the target signal and can be configured in an array to form a directional response
beamforming microphone array - can be designed to be more sensitive to sound coming from one or more specific directions than sound coming from other directions
How can hearing aids reduce noise?
noise affects fatigue, memory, comprehension, and performance because of an increase in cognitive load
digital noise reduction provides less amplification to noise than speech
- identifies frequencies/times when noise is intense relative to speech and applies less amplification
What are the benefits of binaural processing?
better hearing in noise
better localization of sound
phone use going to both ears
What are hearing aid programs?
different settings or configurations of the hearing aid that can be selected based on environment
- vary gain, noise reduction, directionality
number of programs in a hearing aid can vary
What are tinnitus programs?
hearing aids have specific programs for tinnitus patients - patients with ringing or noises in the ears
What is digital feedback control?
whistling sound from the hearing aid is automatically cut out
What are the components of hearing aid fitting and verification?
quality control
electroacoustic analysis
physical fit
fitting approaches
What is quality control?
before fitting the aid
do a listening check using a stethoscope to rule out noise and check sound quality
What is electroacoustic analysis?
hearing aid tested and compared to American National Standards Institute (ANSI) to verify if it meets its intended performance measures
How is the physical fit of a hearing aid tested?
fit of the ear mold or hearing aid is verified with the patient by assessing cosmetic appeal, physical comfort, absence of feedback, ease of insertion, and removal
What are fitting algorithms?
mathematical models that adjust the amplification and frequency response of a hearing aid to match the specific hearing needs of the user
most common: desired sensation level and NAL-NL2
What are real ear measures?
measures the actual sound levels delivered to the ear through the hearing aid
used to set hearing aids/verify proper fitting
- proper frequency gain
- ensure audibility/minimize discomfort
a probe microphone measures sound levels in the ear canal while the hearing aid is in use, hearing aid response displayed on SPLogram
- plots dB SPL at each frequency
How does the equipment for real ear measures work?
place probe tube in ear canal within 5mm of ear drum
measures sound pressure level just before it hits the ear drum, adjust based on target levels
- targets based on hearing loss, hearing aid style, ear shape, etc.
What is the goal of hearing aid fitting?
adjust hearing aid response (using SPLogram) so that it meets the prescriptive targets
connected to manufacturer’s hearing aid software during the fitting and gain adjustments are made in real time
What levels are hearing aid responses calibrated at?
soft - 55 dB SPL
average - 65 dB SPL
loud - 75 dB SPL
max power output - 90 dB SPL
- ensures hearing aid does not exceed uncomfortable hearing levels
What do we do if we notice hearing aid output does not match prescriptive targets?
fine tuning/adjusting the gain to match the targets
can bring gain up at certain frequencies and down at others as necessary
What is the importance of real ear verification?
provides accurate measure of sound pressure level at ear drum which provides more accurate assessment of hearing aid performance
several standards/guidelines insist on use of real ear verification
What are over the counter (OTC) hearing aids?
approved by FDA
hearing instrument, OTC hearing aid, personal sound amplification devices, hearables
Who are OTC hearing instruments for?
for hearing loss treatment
adult and pediatric
mild to severe hearing loss
Who are OTC hearing aids for?
option for treatment of perceived hearing loss
mild to moderate severity loss
adults, not pediatric
What is a PSAP?
personal sound amplification device
for adults to use in specific listening situations such as recreational activities like birdwatching or hunting
NOT for hearing loss, for people with normal hearing
What are hearables?
electronic in-ear devices used for enhanced hearing or as health devices (ex. HR)
for adults, not for children
ear level entertainment, not for hearing loss
How has technology expanded for hearing devices?
AirPod Pros as hearing devices
smart phones as remote controls for hearing aid and “find my” feature
accessories
- remote mics
- streaming devices
