Hearing Aids Flashcards
Name some historical hearing aids.
sound collectors
chair with insert into ear
hairband
battery pack device - body worn hearing aids
Why do some people not want to wear a hearing aid?
There is a stigma surrounding them- however nowadays are hardly noticeable.
What do hearing aids not do?
They do not cure hearing loss.
What are the goals of hearing aids?
Goal is to amplify sounds thereby increasing the signal to the wearer which provides audibility.
Hearings aids are only an _____ not a cure.
aid.
Hearing Aids are not just a mic + amplifier, they have….
complex digital signal processors.
Hearing aids are all different _____, _______ and _______.
Shapes
Sizes
Colours
What is the most common type of hearing aid?
Behind the ear (BTE) (or post aural) Hearing Aid.
How is the behind the ear hearing aid worn?
Behind the pinna.
What is the BTE coupled to?
Its coupled to the concha (main part of the pinna) via plastic tube and earmold.
Where does the behind the ear hearing aid deliver sound to?
It delivers sound to external auditory meatus (ear canal).
What is an alternative to the behind the ear hearing aid?
In the ear.
In the ear hearing aids are better________ but have more restricted ________ than BTE.
aesthetically, acoustics.
In the ear HA’s can be either…
- full concha
- half concha
- ITC (in the canal)
- CIC (completely in the canal)
What is more discrete, in the concha (ear) or in the canal?
in the Canal is more discrete :)
Hearing Aids can be worn on the body, what are these called?
Body Worn Hearing Aids.
When are bone conduction (BC) hearing aids used?
When there’s problems with the pinna, ear canal and glue ear.
What does the bone conduction hearing aid bypass?
It bypasses the outer/middle ear.
What hearing loss can bone conduction hearing aids be used for?
Conductive losses.
How does a bone conduction hearing aid work?
Sound transmitted through mechanical vibration of cranial bones, to cochlea rather than through outer/middle ear (air conduction).
How is the bone conduction hearing aid worn?
On the mastoid process behind the ear and then battery clipped to body (not v. aesthetic).
For babies how is a bone conductor hearing aid worn?
It is worn as a headband.
Why is it important for children to wear hearing aids?
So the child is exposed to sound as early as possible for language acquisition.
Name some issues with bone conduction hearing aids.
- cosmesis of headband- people don’t want to wear it
- headband discomfort (headaches, pressure)
- Restriction of movement
- Low gain, poor sound quality (worse than air conduction HA) and speech discrimination.
- Acoustic feedback
What is a bone anchored hearing aid?
- Titanium screw inserted into skull
- Aid is attached to screw
Name the HA that needs a screw inserted into the skull.
Bone Anchored Hearing Aids.
What sort of patients would use bone anchored hearing aids?
For patients with chronic conductive hearing loss/outer/middle ear pathology.
Bone anchored hearing aids are _______, whereas hairbands are ________.
Permanent
Temporary
What are the components of a hearing aid?
Microphone
Receiver
Digital Amplifoer
What does the microphone of a hearing aid do?
It converts sound energy into electrical energy.
What does a receiver of a hearing aid do?
It converts electrical energy back into sound.
HA process/ feedback loop: 1. 2. 3. 4.\_\_\_\_\_\_\_\_\_\_ \_\_\_\_\_\_\_\_\_\_\_ 5. 6. 7.
Sound wave (picked up by microphone) Voltage wave Digital signal Digital Processing Digital signal Voltage wave Sound wave (delivered to patient)
What performs the following function?-
Signal sampled at discrete time intervals and processed as discrete quantities.
Digital Amplifier.
In the feedback loop of a HA, what happens at the digital processing stage?
Amplified
Manipulated
Define Gain.
Measure of amplification applied to signal (at particular frequencies). Difference between input level and output level.
What is gain set according to?
Hearing Loss.
What gain would be set for:
A mild/moderate high frequency hearing loss.
Mild-moderate gain at high frequencies (presbyacusis)
______ is the most important Hearing Aid (HA) parameter.
Gain
Gain is to do with _______.
Amplification.
How is amplification/gain set?
By applying PTA thresholds to the prescription formula.
Name the 2 types of amplification.
Linear
Non-Linear.
In Linear Amplification, Gain is…
constant for all levels of input.
Linear amplification is ____ input:___ output. (45 degrees)
1:1
Name the amplification:
As the input increases, the output increases at the same rate.
Linear Amplification.
In linear amplification, would a 70dB sound be amplified at the same level as a 40dB sound?
Yes.
What type of amplification is used in modern hearing aids?
Non-linear Amplification.
In non-linear amplification, the gain…
Varies according to input level.
Non-linear amplification:
_____ input: ______ output
What shape is the line and what is this known as?
<1:1
<45 degrees, known as compression.
Name the type of amplification:
70dB sound is amplified at different levels to a 40 dB sound.
Non-linear amplification
70dB would be amplified at a reduced level compared to 40dB.
In non-linear amplification, what does compression do?
Makes sounds more comfortable.
People with ___________ hearing loss have raised hearing thresholds but often their uncomfortable loudness levels remain unchanged (the same as a normal listener).
Sensorineural.
Non-linear amplification performs loudness recruitment, what is this?
Less gain is needed as the input signal increases.
What do we use compression for?
To avoid overamplifying sounds.
We _______ larger input signals to make the output more comfortable.
Compress
What on a HA is useful for different acoustical environments e.g. restaurants, pubs?
Directional microphone.
What assesses input signals and reduces gain in frequencies dominated by noise?
Noise Reduction Algorithms.
What does modulation detection assume?
Assumes noise is more stationary than speech- less gain for stationary inputs.
What does synchrony detection do?
It identifies the presence of speech (harmonics) and rejects other noise.
What can be used in lecture halls that can be connected with a HA?
An Induction Loop
A telecoil pickup - The Loop System
What does an induction loop do?
Inductive pickup in HA picks up signal from induction room around the room and removes background noise by cutting out HA mic.
An ______ loop improves signals to noise ratio and completely removes background noise.
Induction.
Other devices may help patient’s needs better than a hearing aid. What is the proper name for these?
Assisted Listening Devices.
Assisted listening devices can improve _____________ ratio by transmitting amplified sound ____ to the HI listener.
Signal to Noise ratio
Directly
What can assisted listening devices do? give an example :)
Convert sound into a visual or tactile signal.
e.g. vibrating alarm clock.
What are used in hearing impaired schools where the teacher is connected up to a mic and the kids all have headphones?
FM systems.
The patient can use _______ audio streaming that they can ________.
Bluetooth
Control.
What are technology advancements working towards?
Being able to connect HA with smartphones.
Name the 2 parts of fitting a hearing aid.
- Physical and electroacoustical fit
- Follow up and counselling
What provides interface between the HA and the user?
Earmould.
Why is the physical fit of a HA important?
-To facilitate efficient transfer of sounds from receiver to the external auditory meatus.
Physical features can significantly affect the _______ of the hearing aid.
electroacoustics.
What is custom made to suit the individual’s ears?
Earmould.
Why are earmoulds custom made?
- Everyone’s ears are different shapes and sizes
- Poor fit can drastically affect the benefit of the HA
An Earmould should be…
- Comfortable
- Easy to fit and remove
- Cosmetically Acceptable
- Easy to clean
- Good contact for acoustic fit.
Sometimes earmoulds are _______ to help old people to know what ear i’s for (Left and Right are different colours).
colour coded
red- R
blue - L
Why must earmolds must have good contact with the ear?
For a good acoustic fit, otherwise if it didn’t fit properly, sound would leak from the ear.
How do they get the shape of your ear to custom make the earmold?
They put impression material in the ear and leave it to set for 5-10m mins.
What is an open fit alternative to an earmould?
Slim tube and dome.
What are the benefits of the slim tube and dome?
- Low visibility aka. can’t notice it
- Improves ear ventilation (into the eat canal)
- Natural low frequency sounds can enter ear
- Reduces occlusion effect (head in a barrel)
- Comfortable
- Same day fitting
What is a slim tube and dome not suitable for?
Not suitable for more severe losses.
High gain= leakage (sound leaks back out of ear) which causes feedback (whistling).
What do they do for a good electroacoustic fit?
They programme the hearing parameters via hearing aid software which then gives the best HA options.
Level of amplification is also known as _______.
Gain.
What is the most important HA parameter?
Setting Gain.
What should gain be fitted inbetween?
Inbetween hearing thresholds and uncomfortable loudness levels.
The range of sound one can hear is known as the..
dynamic range.
The dynamic range is reduced with __________ _________.
Hearing Impairment.
________ formulas are used to fit HA gain.
Prescriptive.
______ ______ to set gain ares based on real worls data and research.
Mathematical formulas.
Formulas generate __________ ___________of gain required across _______ for a specific set of hearing ________.
target levels
frequencies
hearing thresholds
Formulas are applied using what?
A computer with HA fitting software.
What does the NAL-NL 1 formula aim to do?
Aims to maximise speech intelligibility and restore loudness perception.
The NAL_NL 1 is based on __________________ to predict HI performance.
Loudness models and speech intelligibility index.
Less _______ for loud sounds.
Gain.
What does REM stand for?
Real-ear measurements.
We need to measure the levels of gain reaching the ________ ________.
Tympanic membrane.
What is the purpose if Real-ear measurements (REM)?
To acoustically verify that the correct, prescribed amount of gain is reaching the ear drum.
Why must we do REMs after using our formulas and setting the gain accordingly?
-Everyone’s ears are different shapes and sizes but the prescriptions (formula) only provide an initial estimate based on average.
What checks if we are over or under fitting gain?
REM (Real Ear Measurement).
___________ are a crucial part of hearing aid fittings.
REMS.
What is the method describing:
- small probe placed in ear
- measure level differences with and without hearing aid
- match up measured gain curve to prescribed target
Real Ear Measurements.
What are the 2 main things that should happen post fitting of a HA?
- Patient should build up the use of the HA
- Should attend follow up appointments
Why does the patient need ti build up the use of a HA?
It requires acclimatization, may hear sounds they haven’t heard in years- strange, annoying eg. fridge noise.
Takes time for brain to adjust.
What happens in a follow up appointment?
- Fine-tuning and troubleshooting (making adjustments)
- Outcome measures eg. GHBP- is HA helping? (questionnaire)
A common problem is a poor fitting ________ hurting.
Earmould.
How is the earmould hurting solved?
- make new earmould
- check patient inserting it correctly
- shave bit off earmold
Another common problem is HA whistling, what causes this?
Feedback caused by amplified sound escaping from the ear and is re-amplified by the HA (heard as whistle).
How can HA whistling be stopped?
- earmould not fitting correctly- fit new one, make softer mould to enhance contact with ear
- turn down gain slightly
What can block the earmould and stop/reduce amplified sound being presented to the ear? How is this solved?
Wax
Wash earmould or remove wax if necessary.
Another common problem is ___ tubing/ _______ in the tube- how is this solved?
Blocked
Condenstaion
Insert small vent into earmould to improve air circulation. Or replace tubing.
Why would a narrow bore vent be created in the mould to allow better air circulation?
If the user complains of blocked, sweaty ear canals.
A common problem is that the aid can be too ______.
Loud.
If the aid is too loud, how is it solved?
Reduce overall gain below recommended levels
Once patient acclimitised then increase.
If the hearing aid is too noisy, how is it solve?
- Reduce Low frequency gain (eg. fridge noise)
- Add vent to mold.
When would we reduce high frequency gain?
If aid too tinny.
How are problems with background noise solved?
program HA to allow for directional microphone and increase noise reduction algorithm strength.
What is also important when going through the HA process?
Counselling.
What does counselling involve?
- discuss their problems + problem solve
- we can give them info
- help them deal emotionally
- explain they have to acclimitise to HA
- Manage expectations (its not a cure)
- Set Goals (realistic!)
- Motivation
