Hearing Aids and Implants l Flashcards
Fill in the blanks related to the types of Hearing Loss:
speech information is carried by _____________________________________ (reflecting the movement of the articulators)
speech information is carried by the general shape of speech sounds (reflecting the movement of the articulators)
Each phone requires
__________________________
__________________________
intelligibility is best predicted by ______________________________________
Each phone requires
4 audible octaves or
4 speech features
Intelligibility is best predicted by audibility across a wide range
Hearing aids provide _______________________________________________
audibility across a wide range of frequencies
What does this graph show?
Threshold Shift: Loss of Audibility
We are asking ourselves is this person will be able to understand speech, sharp tunning curve etc.
Looking Closer (SNHL): Audibility and Tuning
Loss of tuning in SNHL
We can’t deal with the threshold shift unfortunately
What should we take into consideration when fitting HA?
Loudness Discomfort Level
You must take into consideration this level when fitting HA, so we need to estimate or predict it
Gain is:
how much things are ‘turned up’
how much sounds are turned up
How much gain to hear 0 dB at 1000 Hz?
Need 30 dB gain (which is a lot of gain to give someone to reach a 0 threshold)
How much gain to hear 0 dB at 4000 Hz?
What does this graph show?
What happens when someone speaks loudly (average level about 75 dB)?
What about the sound of the HVAC?
If the gain was already at 40 dB to reach 0 dB threshold, and someone speaks loudly, you’ll feel 115 dB level which would be TOO LOUD thus far too much gain.
Thus, we don’t really boost to 0 dB.
Speech is about ____ dB at 500 Hz and ____dB at 4 kHz
speech is about 65 dB at 500 Hz, 45 dB at 4 kHz
Speech has a dynamic range of about ____dB
30 dB
Should We Turn All Frequencies Up?
No, because boosting a certain range could cause other frequencies uncomfortable
What does it mean to use Frequency-Dependent Gain?
HA will have this option where you can shape the gain across the frequencies to fit speech in that range
What is compression?
different gain for different input levels
More gain for softer sounds
Less gain for louder sounds
What does this graph show?
It shows how much gain we predict to add speech by taking into consideration discomfort level
What are three features HA have to help shape speech safely?
Frequency-dependent gain
Compression
Output limiting
What are two fitting targets?
DSL
NAL
What is the DSL Approach?
How does the NAL work?
Can even calculate the SII
What is Compression specifically and what could it mean?
range of input levels is compressed into a smaller range of output levels
this could mean:
more gain for soft sounds (better for hearing pins drop)
less gain for loud sounds (more comfort)
What is Compression specifically and what could it mean?
range of input levels is compressed into a smaller range of output levels
this could mean:
more gain for soft sounds (better for hearing pins drop)
less gain for loud sounds (more comfort)
How does compression work?
when a loud input comes in, compression reduces the gain
so compression tends to make things softer
compression + gain increase can make soft sounds louder
What are the two types of compression?
Slow and Fast compression
Describe slow compression:
automatic volume control
can make sounds softer in loud environments
It doesn’t affect the spectral shape
gain is reduced by compressor, compression never has time to release (at least not until speech is finished)
Describe fast compression:
changes dynamic range of speech
can make the softer parts of speech louder
Compression is done in ____________________
Frequency channels
Give an example of how compression is done in Frequency Channels.
Consider the word ‘shoe’
Compressor would turn down gain after intense /∫/
Changes the dynamic range of speech
How does slow compression Affect the spectral shape?
Slow compression doesn’t affect spectral shape
gain is reduced by compressor, compression never has time to release (at least not until speech is finished)
What about fast multi-channel compression?
In the low frequencies, input is low (40 dB)
receives extra ‘soft sound’ gain
in the high frequencies, input is moderate (65 dB)
receives average gain
SPECTRAL CONTRAST is reduced – the shape is distorted
Contrast across frequency changing
over time. This is what tells us how the
mouth is moving, and what the word is
What are three types of in-the-ear custom HA styles?
What are three BTE HA styles?
What are the 5 basic HA components?
What are the processing steps in digital HA?
What are the classic hearing aid problems?
Feedback
Occlusion Effect
Background noise is annoying
Hard to hear speech in background noise
Hard to manipulate small controls
Batteries
Wax
How does feedback affect HA and what is the traditional solution against it?
sound from receiver leaks out of ear canal and enters microphone
this happens over and over again, sound keeps getting louder
traditional solution is to reduce gain in high frequencies (i.e., the high-cut control)
How does occlusion affect HA fitting?
How can we deal with the occlusion effect for HA?
Venting
this has been the standard solution for many years
venting reduces occlusion
“open fit” hearing aids have little-to-no occlusion
What is the difference between open vs closed HA fittings?
How does open fitting affect feedback?
but open fittings make feedback much worse!
Feedback cancellation reduces ______________________________________________________________
feedback and makes it possible to increase venting
What is a sone?
Sones are linear, meaning that 1.0 sone is exactly half as loud as 2.0 sones, and 2.0 sones is half as loud as 4.0 sones. Sones are typically measured in half-sone increments (1.5, 2.0, 2.5, etc.), but there are some cases as products get quieter, where sones will be listed in tenth-sone increments (0.6, 0.7, 0.8, 0.9, etc.)
Open vs Closed Fittings: Everything Leaks!
Even if feedback can be cancelled, large vents reduce the transmission of low-frequency sound
What is the role of detail?
The loss of resolution in SNHL makes it more difficult to separate speech from noise (and from other speakers)
How can we deal with the hearing aid problem that can be hard to hear speech in background noise?
Directional microphones
Adaptive Directional Microphones
Remote Microphone Systems
What do directional microphones do?
Directional microphones reduce sounds from behind (or the side), so it is easier to separate target speech from the noise
In directional microphones, when sound comes from the back, it reaches:_______________________________________________
both sides of the diaphragm at the same time (and is cancelled)
Describe adaptive directional microphones. (3)
typical modern hearing aids use two microphones and electronics to achieve directivity
the directional characteristics can be turned on and off
the directional polar characteristics can be tuned to reduce the most noise
Describe remote microphone systems.
these provide the best signal-to-noise ratio
they allow complete selection of the sound source (which is then much easier to hear and understand)
What are solutions for hard to manipulate small controls dillema?
Solutions for Dexterity Problems:
automatic programs
remote controls
touch-sensitive controls
handles on hearing aids
How can we deal with the battery life hearing aid problem?
- The batteries require a high and consistent current
- Most compact way to do this is to take advantage of the air (as part of the chemical reaction) – zinc air
the sticker prevents this from occurring before use
-Rechargeable Hearing Aids
How can we deal with the wax buildup hearing aid problem?
wax-busters
no-wax systems
behind-the-ear
What are 3 basic BTE non-custom hearing aid styles?
What are the flexible aspects of new hearing aid styles?
Microphone Location
Receiver Position / Sound Outlet
Open/Closed Fitting
Size and Shape
What would be the three possible microphone positions of new hearing aid styles?
Over the ear
In the ear
In the canal
What do microphone in the canal provide?
Concha resonances
Canal resonances
Head-related transfer function (localization)
Natural directivity
No room for directional microphones
What do microphone in the ear provide?
No concha resonances
No canal resonances
Some natural directivity (depends on pinna shape and orientation)
Some room for directional microphones
What do microphone over the ear provide?
No concha resonances
No canal resonances
No natural directivity
Most room for directional microphones
What are the two receiver positions of new hearing styles?
BTE and ITC
Describe BTE receiver position.
Sound must pass through tube to enter canal
Receiver is protected from ear moisture, drainage and wax
Describe ITC receiver position.
Sound delivered directly to ear
no tubing resonances
no protection from wax
Explain how telephone can be used with HA?
telecoils are tiny magnetic coils that pick up energy from telephone receivers or large induction loops
acoustic telephone programs are another option
bluetooth connections are becoming more prevalent
How is data logging done in HA?
how often vc is adjusted, and where volume is left
some hearing aids will adjust start-up volume automatically
what programs are used in what settings
when feedback occurs
how often aid is worn
what the listener’s environments are like
What is frequency transposition?
speech is an abstract pattern
details don’t matter – we can use music as the base
when someone has a precipitous hearing loss, why not move the pattern that they can’t hear onto a lower frequency band
How does Bluetooth Compatibility / DAI help?
this is extremely useful for talking on the telephone and controlling the device
Devices can also be used with DAI
What is binaural integration and how does it relate to HA?
timing and level differences are important for sound localization
hearing aids are constantly adjusting their levels (compression, noise reduction, adaptive directionality, etc.)
it might be useful to synchronize this processing across the ears
