HA EXAM 2
for Loudness summation there is a ___dB at threshold, ___dB at 50dBHL, ____dB at 90dBHL
+3; +6; +9
what is the programability benefit
- adjustments easier to make -electrical programmability allowed for more adjustments to be made
what are the 3 peak clipping methods that were created
-asymmetrical "hard peak clipping" -symmetrical (a little less distortion) -soft peak clipping "peak rounding"
when audibility of HF may not be helpful what 3 things could happen
-cannot deliver HF gain without FB issues -HL is too severe in this range to provide audibility -cochlear dead regions
what are the 3 things related to static compression
-compression ratio -compression threshold -compression range
what is wide dynamic range compression
-compression starts at lower input level -less compression but over a wider range Low knee point Low compression ratio
the 3 disadvantages of DSP (potential)
-dispenser education -time spent programming and reprogramming -cost to patient
when compression is adjusted by means of changing the software what does this mean
-essentially change hardware chip -impacts algorithm of instrument
what are the fig 6 three input levels calculated
-gain for < 40 dB inputs -gain for 65 dB SPL (conversational speech) -gain for 95 dB inputs
what do HA schemes provide (4 things)
-gain reduction for noise -gain enhancement for speech -activation time -SNR and level effects
individual features of DSP aid
-multiple channels -multiple memories -noise reduction -frequency lowering -data learning
what 4 things should we consider when it comes patients and multiple programs
-must consider the person and lifestyle -what are their typical listening situations -can they handle the complexity -can the access the programs (remotes, apps?)
what were the predicted MCLs in Fig 6 done by Pascoe
-normal hearing: mean MCL 65 dB HL -mild loss- 77 dB HL -moderate loss- 90 dB HL -as HL was greater, mean MCL increased
what are the two main things with analog compression
-output compression -input compression
what happens when there is less redundancy for speech for individuals with hearing loss (2 things)
-part of the speech isn't audible -speech may be distorted
who are the best candidates for frequency lowering
-patients who experience speech perception deficits due to insufficient HF audibility in terms of level (an bandwidth) -children or adults? -adults can take advantage of linguistic knowledge, better auditory closure
7 things associated with signal complexity
-precise control over stimulus parameters -feedback management -noise management -multiple microphones -loudness compensation -reduction of instrument noise -simplicity of fitting
conversion involves what two fundamental steps
-sampling -quantization
how do we restore normal loudness growth (how do we manage this)
-soft sounds should continue to be perceived as soft -moderate sounds comfortable -loud sounds loud but tolerable (compression)
what two names does impulse noise reduction have
-sound smoothing -sound relax
what are the 3 frequency lowering terms
-source region -starts frequency -target region
what are the 4 other important factors of the DSP aid
-timing devices/clocks -algorithms -memory -closed versus open platforms
what was the bisection theory
-wallenfels proposed it in 1967 -you choose frequency and gain characteristics for the patient -region between HL and LDL is divided in half from 1k-4k Hz GOAL: maximize speech intelligibility
what are the two most important types of compression
-wide-dynamic range -compression limiting
omnidirectional microphone FBR=
0 (no difference)
Omnidirectional DI
0 dB
Omnidirectional mic AI-DI
0.3dB
What is the Articulation Index (AI) based on this audiogram?
0/100 so 0%
100 dB/100 dB =
1 1:1 needed for a normal hearing person
1 MHz clock stands for and clocks operate in
1 million cycles per second -hundreds of thousands of instruments can be carried out each second -gigaHz range
How are T-rating and M-ratings scaled?
1-4 (4 being the best)
what are the two ways we manage loudness
1. -MPO- maximum power output -OSPL- output sound pressure level 2. -compression
what are the 4 noise reduction strategies for fluctuating noise
1. DSP 2. binaural fitting 3. directional/multiple microphones 4. compression (for faster noise)
what are the 5 noise reduction strategies with constant noise
1. DSP dynamic noise reduction algorithms 2. reduce low frequency amplification 3. directional/multiple microphones 4. binaural fitting (squelch effect) 5. venting (open more, reduce LF)
What are the linear formulas?
1/2 gain NAL
what was the first prescription and who was it introduced by
1/2 gain by sam lybarger- 1944
what are the prescriptive procedures
1/2 gain rule POGO berger NAL
Directivity Index: Frequency specific DI's are sometimes plotted as a graph: for every 1 dB in sensitivity is a ____% change
10
directional mics FBR=
10-30 dB
what is the dynamic range of a normal hearing person
100 dB
Physical Designs of microphones: Electret design provides extended frequency response for what frequencies?
100-15000 Hz
with a loss of 40 dB dynamic range is 100 calculate the compression
100-40 dB= 60 100/60 = 1.6 1.6: 1 (this is what we normally see)
for POGO what frequencies is the 1/2 gain for
1000-4000 Hz
fabry & stypulkowski found that a _____dB re NAL in low frequencies and a boost for high frequencies maximizes______
12 dB speech intelligibility
Super-Cardioid Polar Plot/Pattern has significant attenuation for signals arriving from about _____ degrees to ______ degrees
130; 230
good feedback cancellation algorithms can provide how much gain
15 dB + more stable gain
remote microphones result in a ____ to ____dB improvement in ______
15 to 20 dB improvement in SNR
approximately ____% of people who own HAs don't wear them
15%
Where is the bulk for SII (frequencies)
1500-4000Hz
directional microphones were first introduced when? which included _____% of BTE HAs
1971; 20
when was the first version of the berger developed
1976 and revised in 1984
until when all hearing aid amplifiers were single channel
1987
what ratio = no compression what ratio = lots of compression
1:1 10:1
Directional Microphones: the single cartridge design has ____ microphone(s) and _____ port(s)
1; 2
Many manufactures attempt to achieve a +/- ___ dB from mic
2
Super-Cardioid has _____nulls
2
What does a BiCROS system comprise of?
2 mics, 2 amplifiers, and 1 receiver
What is the typical AI-DI range for directional mics?
2 to 5dB
Occlusion: with a shell in the ear, revit reported pt ear amplifies by ___-____dB
20-30
input increases: 20 dB output increases: 10 dB calculate it
20/10 = 2 ratio is 2:1
input increases: 20 dB output increase: 2 dB calculate it
20/2 = 10 ratio: 10:1
Body Baffle: Erber's study suggested SPL at mic of body aid increased 5-10dB from ____-____Hz. Decreased 5-15 dB from ________-_______Hz and no significant effect above what?
200-800; 1000-2500; 3000
Statistics of T-coils in 2001= in 2021= in Europe=
2001= only 30-40% of HA sold in US had t-coils 2021= ~65% of HA sold in US had t-coils in Europe 85-90% have t-coils
hearing aids perform optimally between
3-6 ft
speech has a dynamic range of what
30 dB
since a 6-10 dB increase results in a doubling of perceived loudness this would result in the pts voice being up to __ times louder and leads to what?
3; rejection
D-Mic: how many inlets? omni-directional mic has how many openings? Hyper-Cardioid (directional) has how many openings? (3)
3;1;2
The FCC requires a t-__/m-___ rating
3;3
typically compressing, shifting or transpose in what frequencies
3k-4k hz or higher
Cardioid DI
4.8 dB
Bi-directional DI
4.8dB
goal of frequency lowering #2
4000 Hz consonant is delivered to the patient at 2000 Hz, it won't sound the same, the altered signal may be better than not hearing
Maximum sensitivity for cardioid is ~_____ degrees
45
for flat audiograms (between .5-4 kHz) how many channels do we need
5-8 channels (2-4 channels would do a decent job)
Supercardioid DI
5.7dB
Directivity index is calculated at
500, 1000, 2000, 4000Hz
SNR with a 50db loss= with a 80db loss=
50= +6 80= +12 with each 1dB improvement in SNR you get a 10% improvement in word recognition
What is the Articulation Index (AI) based on this audiogram?
56/100 or 56%
Multiple Microphone Arrays: more than __ does not result in greater benefit. Hearing aids fit today, utilize a "microphone array" ___ mics, two on each aid
5; 4
Hypercardoid DI
6 dB
Occlusion: a ___-___dB increase results in a doubling of perceived loudness
6-10
Sound shadow/head shadow: fairly significant reduction, Near ear-far ear = ___dB difference for spondee words
6.4
music has a dynamic range of what
60 dB
Ear canal resonance: ears reach adult like resonance at what age?
7
study suggests how many channels are needed to match prescriptive targets
7 channels -with 90% or better accuracy
for sloping, precipitously sloping and rising configurations how many channels are needed
8-16 channels
Occlusion: a 2mm vent results in a decrease of about ____dB at 200 Hz
8.5
what percentage of people with aidable HL will benefit from dir mics
80-90%
what is the nyquist frequency for speech
8000 Hz x 2
Bi-Directional: Nulls are present at _____ and ______ degrees
90; 270
What is the Articulation Index (AI) based on this audiogram?
92/100 or 92%
in 2013 _____% of aids dispensed were DSP
98.6%
> the noise?
> the reduction in intelligibility (most difficult with topic change)
Which class of amplifier is the oldest, least expensive, and does not produce a lot of gain
A
What are the three classifications of the final stage amplifier?
A, B, D
Both head and body can rearrange sound waves (as well as clothing) and is more critical for body aids but is now used for what?
ALDs
Subtracts electroacoustic parameters based on what? (6)
Age Gender Experience level Severity of loss Native language Individual differences
What is the SPL-o-gram?
An audiogram that has LDLs and fitting targets
what type of method is DSL?
An output method
Waveforms that mimic acoustic waveforms they represent
Analog
What does AI-DI and SII-DI index stand for?
Articulation index and speech intelligibility index
Individuals with hearing loss have a loss of __________ and _________ can occur
Audibility; Distortions
Which Class of amplifier is referred to as push-pull circuit?
B
What are the 6 hearing aid styles we need to pay attention to?
BTE, ITE, Canal, CIC, RITE, IIC
What is the benefit of T-Coil?
Background sounds are not amplified so signal-to-noise ratio improves from telephone conversation
What type of polar plot is this?
Bi-directional
What are the two secondary polar plots/patterns?
Bi-directional and Supercardioid
Higher Order Directional Mics: are used today in all major manufactures HAs and work how?
Binaural wireless technology combines two mic's on each aid
What is a BAHA?
Bone anchored hearing aid
DSL 5 accommodate for comfortable listening in what?
Both quiet and noise
What is the main difference between a CROS system and a BICROS system?
CROS: better ear is normal to mild high frequency loss. BICROS: better ear is mild to severe hearing loss
How do D amplifiers differ?
Can produce higher outputs, decrease distortion, extend high frequency emphasis, lower battery consumption and smaller size
What type of polar plot is this?
Cardioid
What is the squelch effect?
Central Auditory Nervous system compares and integrates different signals being received at each ear.
DSL Who it's used for? How much gain?
Children- bc want them to make all speech sounds audible Pts with sudden HL - can handle more HF gain bc are used to normal hearing Has the most gain
How do omni-directional microphones work?
Closed box divided into two chambers by a thin diaphragm, sound enters through the mic port, sound pressure changes causing the diaphragm to vibrate and the vibration creates an electrical signal
Describe the pathway from communication strategies to cochlear implants
Communication strategies -> PSAP -> ALD -> OTC -> prescription HA-> cochlear implants
DSL 5.0 Optimize protocols for what?
Compression circuitry
What are the different physical designs of microphones?
Condenser microphone, carbon, electromagnetic, ceramic, Electret, and Microelectromechanical system
Manipulation of Polar Plots is doing what?
Constantly changing
DSL5.0 maximizes number of acoustic cues contained in what?
Conversational speech
How do you determine AI based on dot audiogram?
Count number of dots that are audible (above patient's threshold)
For children and suspend onset HL which formula?
DSL bc provides more HF gain that is needed for children speech development and sudden loss pt are used to the sound of normal speech
Individuals with hearing loss have a(n) __________ (easier/difficult) time in noise
Difficult
Represents signals as a string of numbers
Digital
What are the two different ways we can manage difficulty in noise?
Digital noise reduction and directional microphone technology
What is the the only thing we can do to improve SNR
Directional Microphone Technology
Duel-Microphones: output from one microphone can be delayed electronically and then subtracted from the first. This results in what?
Directional Response
Directivity Index: the higher the DI, the more what?
Directional it is and more likely will do well in noisy environments
A lot of gain and can cause what?
Distortions
NAL-NL2: as HL becomes worse in degree and slop what happens to speech?
Distortions
Digital Noise Reduction (DNR):How does Speech Enhancement technology work?
Drags noise to the envelope of speech
What type of microphones are most common today?
Dual-microphones
NAL-NL1: audibility vs effective audibility
Effective audibility - how much information can be extracted from speech sounds
Physical Designs of microphones: this type started in 1960's and is still used today
Electret
Physical Designs of microphones: which design is made by a thin metal?
Electret
Digital Noise Reduction (DNR) changes output to do what? (2)
Enhance speech and attenuate sound
NAL-NL 1 attempts to _____ rather than preserve the loudness relationships amongst speech frequencies
Equalize
Why is AI-DI range for direction mics important?
Every dB improvement in AI-DI results in an increase in speech understanding of 10%
DSL 5.0 objectives: avoids what?
Excessive loudness
sounds will not hit diaphragm simultaneously, diaphragm vibrates and electrical signal results so how does this get resolved?
External port delay
What do Bi-Directional polar plots pick up?
Front and back Equally
How does the brain dictate the primary sound source? (7) things
Fundamental Frequency, Harmonic structure, Suprasegmental (stress, tone, loudness), Location, Timbre, Rate, and Visual cues
For NAL targets for someone with precipitous sloping there will be no targets in the higher frequencies, but this does not mean there is no_____
Gain
NAL-NL1 fitting method is considered what kind of method?
Gain method
Dual-Microphones: have _________(less/greater) flexibility
Greater
adaptive polar plots
HA automatically samples all polar plots and determines which are around the patients should be maximally reduced
what happens when fixed release times are too short
HA will go in and out of compression often
fig 6 said for gain at 40 the formulae was designed to correct hearing to
HL -20 dB -20 dB
Disadvantages of Eye glass aids (2)
Heavy and inconvenient to repair
With N AL, we see a sharper decline in ____ frequencies
High
The SII has more weight given to ________ frequencies
Higher; 6000-8000Hz
Directivity Index: Which Polar Plot/Pattern has the best response to manage noise in those environments and what is the DI index?
Hyper-Cardioid; 6dB
What type of polar plot is this?
Hyper-cardioid
One directional microphones can be known as what?
Hyper-cardioid polar pattern
what type of Polar Plot/Pattern tends to be/have the best response with hearing aid use
Hypercardioid
sampling rate is expressed in
Hz
the other 2 formulae for digital hearing instruments
IHAFF- independent hearing aid fitting formula fig. 6- figure from article
which hearing aid is placed and removed by a professional?
IITC (invisible in the canal)
For ____ need to mark ear mold impressions to insure mic openings are in line
ITE's
What does "in Situ" mean?
In place- includes factors that influence output
Compression ratio is _____ slightly for mild-moderate losses
Increased
NAL-NL2 differences: _____ gain for adults than NL 1
Less
___gain for adults at ____ input levels
Less Loud
What is the major difference between an NAL - NL2 and NAL - NL1?
Less gain in NL2
New version of DSL(v 5.0) accounts for what?
Limitations in noise Establishing MPO to maintain user comfort
NAL-NL1 What it's used for? How much gain?
Long term users - bc prefer more high freq gain Men? - prefer more gain Has more HF gain
NAL-NL 1 prescribes ______ frequency gain than most other fitting methods and less ______ frequency gain for severe hearing loss than other prescriptive methods
Low high
What is the difference between directional flat and directional low-cut filtering?
Low cut provides more reduction of low frequency amplification
What is a problem with directional mics?
Low-frequency roll-off
What does the "m" and "I/o" stand for in DSLm[i/o]?
M- multilevel family targets (based on age and etiology) I/o- input/output level
Why do we want to use Volume control if HAs adapt?
MCL varies due to auditory fatigue, changes in ET function
T coils concert ____ energy to____ energy
Magnetic to electrical
NL 1 fitting method: provides gain recommendations that do what?
Make loudness of speech bands equal across a wide band of frequencies
What is the primary goals of NAL formulas? (2)
Maximize speech intelligibility Using predictive models for speech intelligibility
What are the goals for NAL-NL2 (2)
Maximize speech intelligibility for levels around compression threshold Keeping overall loudness at or below that of normal listeners
Physical Designs of microphones: Which design is only used in Starkey hearing aids?
Microelectromechanical systems (MEMS)
Higher Order Directional mics: includes what?
Microphone Arrays
Previous users prefer _____ gain then new users
More
For DSL: we have ______ HF and ______ LF compared to NAL
More More
Makes prefer _____ ______ then females
More gain
BTE Directional Hearing Aids: instead of completely covering the microphones, how is it managed now?
More of a hood, moisture rolls off but microphone still exposed
The more HF we give what happens to the pt perception
More uncomfortable
For reoccurring patients which formula
NAL 1
For first time users and geriatric patients what formula
NAL 2 bc provides less gain
what is the order of how NAL was revised
NAL, NAL-R, NAL- RP (correction factor)
Nal- Nl2 Who it's used for? How much gain?
New users with gradual hearing losses - easier to adapt bc less HF gain Geriatric patients- easier to adapt bc less HF gain Least amount of HF gain
When looking at NAL targets for someone with precipitously sloping you will see what?
No targets in the higher frequencies
Principal of DSL: what does it do for loudness?
Normalizes it Perception would be like a normal hearing individual
What is the ability to utilize the opposite ear to the sound source to hear signal?
Off-Side hearing
What type of polar plot is this?
Omni-directional
What are the three primary polar plots/patterns?
Omni-directional, cardioid, and Hypercardioid
What are the different classes of hearing aid microphones? (4)
Omni-directional, directional, dual microphones, and microphone arrays
When to use Omni versus Directional mics?
Omni: talker located other than front, background noise absent/quiet, smaller rooms. Directional: talker located in front, moderate background noise, larger rooms
Dual Microphone (D-Mic) design has what type of mics?
One omni-directional and one directional within the same capsule
DSL method: what is the primary interest?
Output at TM (not gain)
Who are PSAP used for?
People with normal hearing
What does PSAP stand for?
Personal sound amplification products
Which hearing aid company is big into CROS systems?
Phonak
Microphones are classified by what? (3)
Physical Design, Classes of microphones, and Polar patterns (or plots)
What is the primary purpose of the T-coil?
Pick up signal from telephone receiver
How do hearing aids work in noise?
Picks out speech rather than noise (not always the case)
What classification of microphones is most important to know?
Polar Patterns (or plots)
Microphones can be characterized through what?
Polar Plots
What are the 3 stages of amplification for HA's?
Pre-amp associated with microphone, processing stage, output stage
The ear canal resonance can also be known as what?
Preamplifer
The brain can manage a complex waveform by sorting through what is important to us. We can track one voice in the presence of another is called what?
Primary sound source
If the patient does not have a smart phone and dexterity issues, what can we do?
Provide a remote
What type of HAs have always had directional microphones?
RICs
Microphone techniques: Evidence supports what?
SNR improvement
What is SNR?
SNR needed for HIP to achieve 50% word recognition scores compared to people with normal hearing
What do Supercardioid polar plots pick up?
Same as hypercardioid but reduces sensitivity
Dual-Microphones: what is managed digitally?
Signal delay and subtraction
NL 1 fitting method: what are gain targets for soft, moderate, loud inputs?
Soft- 50 dBspl Moderate-65 dBspl Loud- 80 dBspl
Directional Microphones: how does the single cartridge design work?
Sounds from the two ports arrive on either side of the diaphragm
What is Multi-Speaker Access Technology?
Speech Enhancement technology
What is the difference between hyper-cardioid and super-cardioid polar plots/patterns
Super-Cardioid is less sensitive in the back
What type of polar plot is this?
Super-cardioid
Dual-Microphones (D-Mics): a switch is located on the faceplate of some aids to do what?
Switch from omni-mode (in quiet) and directional (in noise)
NAL non-linear version 1 and 2: originated from? Evolved from what?
Sydney Australia Linear based formula NAL-R
Individuals with severe to profound loss depend on what cues?
Temporal and amplitude
What are the three cues for speech importance?
Temporal, Amplitude, Frequency
What affects the timing of the signal?
The damper
Directional Microphones: the bigger the case the more you can separate the microphones so what dose this mean for custom products?
The smaller we go, the harder it gets to separate
Not everyone with hearing loss will not be able to use what?
The temporal, amplitude, and frequency cues
Patients mist be able to do what in their instrument?
Tolerate gain
Frequency dependent gain for tonal vs non-tonal: what is the difference?
Tonal- changes meanings in language that does not occur in English
How can we counsel patients about polar plots?
Train them to look where the sound is coming from
What are DSL factors that influence fitting? (3)
Transducer for testing Ear canal resonance Style of hearing aid
Describe Dual-Microphones
Two separate omni-directional microphones, each has its own separate inlet
what is IHAFF also referred to as
VIOLA -visualization of input/output locator algorithm
DSL i/o was developed to address
WDRC hearing aids
expansion has lower knee point than what
WDRC kneepoint
what is compression
a monitoring circuit built into the hearing aid
explain loudness growth for a normal hearing person vs SNHL
a normal hearing person hears soft sounds as soft. with a HL it takes more intensity to just barley hear those soft sounds therefore we need to amplify them just to hear those (this is the critical reason on why we fit hearing aids) sounds (the graph)
for remote microphones a 15 to 20 dB improvement in SNR is translated as
a significant improvement in speech intelligibility -1 dB improvement in SNR results in 7 to 10% improvement in performance
what are adaptive polar plots best with
a single noise source
what are programmable aids
a system that allows for programming, reprogramming and changing frequency response, gain, maximum output, and some compression characteristics
Dual-Microphones: describe the pathway
acoustic to electrical energy then combined electronically
_______ processing by premium features can potentially improve scores on tests in lab
acoustical
Volume controls (VC) allows users to do what?
adjust amount of gain they are recieveing
who can understand speech in moderately noisy environments
adults
AI-DI/SII-DI Adults= Children=
adults= when speech intelligibility is at or less than 80% it is important to start talking to adults about hearing instruments children= when speech intelligibility is at or less than 80% they should DEFINITELY be fit with amplification
receivers used with HAs
air conduction bone conduction output transducer convert an amplified electrical signal back to an acoustical signal
SII-DI 1.0=
all of the speech information is both audible or usable
What was the phonak watch pilot?
along the face, you can press up or down for volume control
what is the rationale of the berger prescription
amount of gain provided should amplify sound to average speech spectrum level (55-75 dB SPL)
sounds below the expansion kneepoint are
amplified less
T-Coils: when two wires are close (in phone or other coupling device and in hearing aid) what happens?
an electromagnetic field is created
What type of programming are IITC?
analog
what should we know about the anti-aliasing filer
analog low pass filter- required at the beginning of the processing chain to fulfill the sampling theorem
modulation based schemes
analyzes signal for # and depth of modulations (speech usually has 4-6 modulations per second)
what two major things do we have to keep into account when selecting a HA selection
anatomical and visual/dexterity issues of pt
What are Microphone arrays?
any device that has more than 3 MICs if a patient is fit binaurally
digital noise reduction
any type of scheme in which a mathematical calculation is employed by the the hearing aids signal classification system to separate a desired signal (typically speech) from an undesired signal (typically background noise)
what is the goal of a linear aid
apply significant gain so normal conversation is around the middle of the HIP dynamic range
What is the baffle effect?
as sound approaches any obstacle, rearrangement of sound waves occue
what is the minimum sampling frequency for speech & what does this mean
at least 16 kHz -means the value of the voltage that represents the sine wave is measure 16,000 times per second or once every 62.5 msec
receivers used with HA: bone conduction (soft band) used for individuals with
atresia or stenos or chronic middle ear disease with drainage (makes regular HA impossible)
goal of frequency lowering #1
attempt to make HF speech signals ("s" "sh") audible at a lowering frequency
DNR attempts to do what when speech is dominant
attempts to clean up the speech signal when it appears to be dominant (+2-5 dB S/N)
according to the formulae gain overcomes what that is caused by the hearing loss
attenuation
what does attenuation stand for
audibility
goal of frequency lowering #3
auditory training may accelerate acceptance
What is an advantage of binaural hearing aids?
avoid sensory deprivation
When class D amplifiers are used in analog aids, where is the amplifier?
built into the case of receiver so less space
What is a CROS hearing aid?
contralateral routing of signal
What is RITE best for? (2)
cosmetics and gain/output
What are CIC aids best for? (2)
cosmetics and telephone use
Class D amplifiers cause a ________(decrease/increase) in distortion
decrease
TK control for pt complaint for not hearing at distance
decrease TK: so they can hear
Volume control: On BTEs, turning rotary VC down ________gain and turning it up ________gain
decrease; increase
As the t- and m- rating increases, what happens to interference?
decreases
What is the M-rating?
describes the level of hearing aid microphone compatibility within a telephone
How does a T-coil work?
detects and converts magnetic energy into electrical energy
automatic acclimatization
determine a prescribed amount of increase in gain and when that will occur (we can tell the HA when to change settings on what date..ex if pt is going out of town and we want full gain on set date)
who was the desired sensation level created for
developed for fitting infants/ children with linear amplification
Physical Designs of microphones: condenser microphones, carbon, electromagnetic, and ceramic _________(did/did not) do a good job in hearing aids
did not
for multi-channel processing we apply what
different compression characteristics to different frequency specific inputs (aka larger band widths)
Microphone techniques: are designed to be more sensitive to sound arriving from what?
different directions
what are programmable aids NOT
digital hearing aids
comfort in noise is affected by
digital noise reduction
what are programmable aids called
digitally controlled analog hearing aids DCA
speech intelligibility in noise is affected by
directional microphone technology
don't use what for music
directional mics
what is clinical proves for improving signal to noise ratio
directional mics
what is the only special feature that is widely proven to improve speech recognition in the presence of background noise
directional mics
Advantages of RITE? (2)
directional/dual mics and cosmetically appealing
Advantages of BTE?
directional/dual mics, power
directional microphones also helps noise because of
directionality and low frequency roll-off
Directivity Index: speech arriving from 0 degrees means what to the patient?
directly in front
Where are receivers located on BTE's?
directly underneath the ear hook
with the linear amplifier saturation is created causing what
distortion- this is what we can control
what is the ballpark compression ratio
divide residual dynamic range of normal hearing individual by residual dynamic range of the HIP
Dual-Microphones (D-Mics): ______(do/do not) fit on canal aids
do not
Polar Plots: Current Polar Plots: Current DSP (Digital Signal Processing) HAs are what?
dynamic and adaptive in the environment
what was the point of NAL
equal loudness across frequency bands
Omni-directional is __________sensitive to the arrival of sounds from all directions
equally
What do Omni-directional polar plots pick up?
equally all around
what is the sound aliases
essentially low-pass filter is placed before the A/D converter
definition needed to know for directional mics and S/N
every 1 dB of improvement in S/N expect 7-10% improvement in speech intelligibility (less improvement for more severe losses)
for the binary what happens
every time a doubling occurs, an additional 0 is placed at the end of the string
Advantages of CIC? (2)
excellent position for microphone and most cosmetically appealing
what was the negative consequence of WDRC
excessive amplification of low-level input signals increases audibility of low-level environment noise and noise generated by hearing aid
what was the first non-linear perceptive formula
fig 6 -killion and fikert-pasa (1993)
what are the "big three" non-linear prescriptive fitting formulae - what we use today
fig 6 IHAFF desired sensation level
what is proven to preform equally well
fixed and adaptive dir mics
what is the greatest benefit of the DSP aid
flexibility!! we can make so many changes on site!!
what can stable gain make a big difference on
for speech audibility and improve intelligibility
speech shaped intensity is on what spectrum
frequency
sampling is how the _____and____ of sound become represented by numbers
frequency and intensity
what feature on DSP aids do manufactures choose
frequency lowering (compression, transposition)
What do Hypercardioid polar plots pick up?
front and back ( but more emphasis on front)
What do cardioid polar plots pick up?
front and sides but not back
power of receiver accommodate different hearing loss and varies by what?
gain
if noise is dominant what happens in DNR
gain for everything is reduced
What are BTE best for?(2)
gain/output and directivity
gain for mild and moderate example with a moderate loss
gain65= 90 dB (mean MCL for moderate HL) - 65 dB (normal conversational input) = 25 dB gain
The __________(greater/less) the hearing loss, the less importance frequency cues play
greater
What was the problem with phonak watch pilot?
had separate batteries and when one died, you were screwed
Disadvantages of BTE? (2)
harder to manipulate and susceptible to wind noise
Disadvantages of RITE? (1)
harder to manipulate due to flexibility of wire
Cardioid Polar Pattern is _______shaped and more sensitive to sounds from the _________ than the ________
heart; front; back
Class D Amplifiers has an extended _____(low/high) frequency emphasis
high
Ear canal resonance: smaller canal = more what?
high frequency amplification
what does the compression limiting consist of
high kneepoint high compression ratio
Ear canal resonance: results in an increase in amplified sound in the ______ frequencies _______-_____Hz
high; 2000-4000
Class D amplifiers can produce _______(lower/higher) outputs
higher
speech is
highly redundant (adults have good auditory closure skills)
SNR and level effected
how much noise reduction (10 dB) and when does it start (with 60 dB SPL of noise or 80 dB SPL of noise)
what is compression ratio
how much the signal is being compressed
Polar Plots are used to dictate what?
how sensitive a hearing instrument to different sound sources
how is the signal analyzed in each channel of the HA
if classified as noise, signal is reduced, if classified as speech, signal is enhanced
Microphone techniques use outputs from 2 or more mics which do what?
improve SNR through spatially dependent sound sensitivity
Directivity Index: the ability to do what?
improve the SNR in a diffuse noisy environment with speech arriving from 0 degrees
TK control for pt complaint for feedback
increase TK
TK control for pt complaint for breathy sounds
increase TK: to reduce the gain
for music we increase what
increase the dynamic range to ensure output set to patients tolerances
Volume control: On ITEs turning wheel toward noise/face ________volume. Turning the wheel toward the back of the head ________volume
increase, decrease
what does IHAFF stand for
independent hearing aid fitting formula -12 audiologists
what = output
input + gain, which is at the eardrum
for the linear amplifier what two things are increased and at what degree
input and output are increased simultaneously at a 45 degree line
What is loudness summation?
input from both ears is summed by the brain
what is 1:1 ratio
input increases by 1 output up 1
10:1
input increases by 10 output up 1- this is considered a lot of compression
Low-Frequency Roll-off: gain compensation for directional mics ________(is/is not) necessary for patients with good LF hearing
is not
dynamic range
is the ratio of the maximum signal level to the minimum signal level (example 115 dB SPL- 25 dB SPL= 90 dB dynamic range)
Why are magnetic receivers the weakest link in hearing aids?
it is susceptible to both wax and moisture
what is the DSP definition (what 7 things can it change)
its a system that digitizes sounds and allows for programming, reprogramming, and memorizing frequency response, gain, maximum output, and compression characteristics
what is bluetooth technology and how well does it work up to ft wise
its cord replacement, works up to 30 ft
What is a rotary volume control?
keeps rolling up even when limit is hit
Ear canal resonance: since smaller canals have high frequency amplification what does this mean?
kids will have an intolerance to HF
Custom products: the further we separate the mic and receiver the ______(more/less) feedback
less
For loudness summation _____(less/more) gain is needed
less
ITE Directional Hearing aids: ______(less/more) effect of the directional microphones on these devices
less
Physical Designs of microphones: Electret design is made with a thin metal which is ________(less/more) sensitive to vibrations
less
what does hard-wired mean
less ability to make changes to the HA -the manufactures can only pick this
wide DR=
less compression & happens sooner
Disadvantages of canal aids?(3)
limited amplification, small controls/batteries and cannot be used for small ears
Disadvantages of CIC?(5)
limited amplification, small controls/batteries and cannot be used for small ears, no directional mics and deep canal fitting required
Disadvantages of ITE? (3)
limits to power ,susceptible to wax, and more occlusion effect since less room for venting
1:1 is what type of aid
linear
clinically NAL-R was the most widely used approach for
linear amplification
several prescriptive formulas were developed for what
linear amplification
below compression threshold, most hearing aids amplify
linearly
why is frequency lowering important for female voices
listeners need audibility up to 9000 Hz to differentiate /s/ versus /sh/
Having two ears allows us to what?
localize
linear DR=
longer, more compression & happens faster
what does DNR do to clean up speech
looks for gaps between speech signals, and reduce the noise for these gaps
what does the classification system of the DNR do
looks for very sharp peaks in the onset signal, sound is reduced giving that noise a duller sound
What is the vertical t-coil used for?
loops
IHAFF wanted to complete what scaling and relies on what
loudenss -relies strongly on direct loudness measurements
compression limiting (output) is used for
louder inputs
what is the biggest thing we have to manage
loudness
what are the advantages of binaural hearing? (4)
loudness summation, off-side hearing, localization and avoid sensory deprivation
With an electronic device, you will pick up a _______(low/high) level sound/noise
low
TK adjusts over a range of what and where is its linear gain
low inputs from 40-60 dB SPL -linear gain is below the kneepoint
what does the wide dynamic range compression consist of
low kneepoint low compression ratio
start frequency
lowest frequency in the source region (like compression kneepoint) 3000-4000Hz. 3000 Hz start, 4000 Hz the target
If you do not have a t-coil what should you do to the hearing aid? (2)
maximize frequency picked up by telephone between 300-3000Hz or you can create a program
Auto phone/easy phone: some telephones have small magnets which will not trigger the switch. What can we do?
may need to add magnet onto the telephone headset
What is the articulation index?
measure in percentage of normal conversational speech which is audible
Where is all the hardware for a CROS system? (2)
mic is on bad ear and hearing aid is worn on normal hearing ear to receive signal
what is expansion referred to as
microphone noise reduction
Why do we have multiple microphones? (separation between the two)
microphones pick up and compares and chooses best option
berger and 1/2 gain tended to over amplify what type of hearing loss
mild to moderately-severe HL
What is a t-coil?
mini antenna; small electromagnetic induction coil (copper)
Disadvantages of Through-the-ear aids? (2)
minor surgery and adverse directionality
What degree of hearing loss is recommended for t-coils
moderately severe-profound
The greater the HL the ________(more/less) the SNR needs to be
more
The lesser the distance the _____ roll off you will have
more
the higher the ratio the
more compression
speech has fewer modulations with
more depth than noise
DSL provides overall
more output than other fitting methods -more low and high frequency output
Are t-coils programmable?
most DSP aid entry to premium level can be programmed and most auto phone programs work off base program
audibility and comfort in quite is affected by
multiple channels of WDRC, expansion & frequency lowering & adaptive feedback suppression
DCA and DSP hearing aids can have
multiple memories
convenience, ease of use and simplicity is affected by
multiple memories, signal classification, & trainability
what program could increase if patient is consistently turning it up
music
what does NAL stand for and when was it introduced and then when was it revised
national acoustic laboratory (what we use today) -1976, 1986- NAL-R
Through-the-ear: open fitting maintains what?
natural ear resonance
advantages of canal aids?(2)
natural position for microphone and cosmetically better than ITE
wireless HA to HA communication is
near field magnetic induction- NFMI -low power, short distance
Advantages of Through-the-ear aids? (3)
no occlusion, no heat/moisture build up and no discomfort from mold
when the circuit reduces the gain what doesn't occur
no peak clipping or distortion would occur
what did evidence support with premium technology
no statistically significant difference in outcomes between premium and basic-feature devices
CROS systems allow for what?
noise reduction
SII-DI 0=
none of the speech information is audible or usable
What are canal aids best for?
nothing
the binary implies the use of
one of two numbers either a 1 or 0
what is the name of the BAHA used today?
osseointegrated implant
what was the first commercial DSP aid
oticon digifocus- 1996
what method is DSL considered and who is it generalized to now
output method -generalized to adult population
What is the front-to-back ratio?
output of hearing aid in response to a speaker placed at 0 degrees minus the output of a hearing aid in response to speaker placed at 180 degrees
what = input
output-gain
what = gain
output-input
signal classification is taking whats going on around & changing what types of things
overall SPL, frequency-specific SPL, modulation rate, amplitude depth
source region
part of the spectrum where information is moved from
target region
part of the spectrum where information is moved to
Who used a BiCROS?
people with HL in better ear and an unaidable hearing loss in the other
what can be modified but only those that the manufacturer allows
performance parameters
what is stable gain
person can talk, eat, move around ect. and the HA will not go into FB
What is the horizonal t-coil used for?
phone
How do you have to position the phone with a t-coil?
phone receiver up and back
What is an issues with T-coils?
placement of coil varies in hearing aids
What are some disadvantages of t-coil?
placement varies, noisy, very steep LF roll off
what is the compression threshold/kneepoint
point where compression starts
Hearing loss causes sound to be what?
poorly defined within the cognitive system
Advantages of body aid(2)
power and durability
what does POGO stand for
prescription of gain and output
algorithm=____which is
prescription....which is a mathematical rule or process to solve a problem
multiple memories is known as what and can do what
programs and can manage different listening environments
what is the assumption when mirroring the audiogram...if the patient has 45 dB HL
provide 45 dB of gain to move threshold to "normal"
what is the goal of a compression aid
provision of progressively less gain for greater input intensity levels (aka squash it all into a small dynamic range)
Who uses a CROS system?
pt with unilateral loss with normal hearing on other side
Who are OTCs for?
pts with mild-moderate loss
What are class D Amplifiers also known as?
pulse-width modulated amplifier or switching amplifier
Where are class C amplifiers used for? HA's
radio transmitters, no
for music we raise what
raise compression kneepoint- we make it more linear
what is compression range
range of inputs where compression occurs
What is the directivity index?
ratio of sensitivity for frontal sounds relative to the sensitivity averaged across all other directions. measures how directional the hearing aid is
What is Beta (single cartridge design)
ratio of the internal time delay to the external time delay
expansion allows for signals below first TK to
receive reduced gain rather than maximum gain
TK for greater gain
reduce the input we get more of a gain
venting ________(reduces/enhances) the directional effects.
reduces
with expansions when reducing low level environment sounds it also
reduces low level speech
what was the goal of IHAFF
restoration of normal loudness perception
beyond 6 ft of a hearing aid what happens
reverberation and the inverse square law lower the signal to noise ratio
what is important as mic ports start becoming clogged and what might happen
routine maintenance -this will affect performance of mic
What is the auto phone/easy phone?
same as other t-coils but use a magnetic reed switch (not programable)
what was carharts comparative methods goal with HA selection in 1940s
select a HA that provided maximum benefit using a speech method
Class B amplifier has separate amplifiers that do what?
separate amplifiers used to amplify the positive portion of signal and negative portion of the signal
Super-Cardioid has a smaller lobe at 180 degrees, but the lobe is _____________ and _____________ that that for the hyper-cardioid
shallower; narrower
what did thornton-raffins evidence show with speech scores
showing two speech discrimination scores need to be very different to be significant
what does the signal of the multi-channel do
signal splits into various frequency bands- passes through separate circuit paths
What is a Trans Ear Bone Conduction Hearing aid used for?
single sided deafness
For the baffle effect, the amount of change in sound intensity will depend on what 4 things?
size of obstacle, angle of incidence, material of obstacle, and flatness of obstacle
WDRC (input) is used for
soft inputs
TK for less gain
softer inputs
what can allow the hardware to do more or different things
software updates
improved speech intelligibility
some evidence now supports improved speech indelibility with use of DNR
How does through the ear aids work?
sounds delivered to outer ear canal through a titanium tube inserted into soft tissue
How does the Trans Ear Bone conduction aid work?
sounds received on dead side and signal is transferred to opposite side via BC
what is the negative part with phase cancellation
sounds that may not be FB is detected and then would create actual FB- sending an out of phase signal
different programs are used for
specific listening situations
what was the goal of prescriptive fitting formulae early methods: what was the focus
specify the performance characteristics of the patients HL -gain was the focus (most concerned about audibility)
what should be lowered if patient is consistently turning the gain down
start-up gain
what are the compression characteristics
static dynamic
What is the T-rating?
t-coil compatibility within a telephone
Advantages of ITE? (2)
takes advantages of pinna effect and easier for pts to manipulate
what is sampling
taking pictures or snapshots of the signal at evenly spaced intervals -the rest of the waveform is discarded -few samples or many samples
What are ITE's best for? (1)
telephone use
sampling rate =
temporal aspect
what is compression limiting
the HA amplifies linearly until you get to high output levels High knee point high compression ratio
what happens when fixed release times are long
the HA will continue to compress after loud sound ceases
what is frequency response
the amount of response from the gain
with compression what better fits the patients hearing loss, this is our goal to fit for the pt dynamic range
the changes of the amount of gain the HA circuit adds to the input signal
what is the basic component of any DSP system
the clock
with ratio HIP the greater the loss
the greater the compression ratio needed
what is it called when compression begins
the knee point
why is input compression intended for mild-moderate SNHL
the larger dynamic ranges (MPO fluctuates)
what is the null of the polar plot consistent with
the location of the noise source
what did DSL find
the long-term average speech spectrum consisted of more low-frequency energy and less high frequency energy
When talking about Lobes and Nulls, which is the blind spot?
the null
the sampling rate indicates what
the number of samples that are taken during one second
why is output compression used for children
the output controlled to allleviate chance of reaching damaging output levels
turning down VC constantly can be bad because
the patient may never adapt to prescription
what is MPO/OSPL defined as
the point at which hearing aid stops increasing amplification
what is the process that must occur with sampling
the process that must occur during which the continuous acoustical signal is converted into discrete digits
what is "squeezes"
the range between soft and loud speech into the residual DR
what do linear aids provide
the same gain regardless of the input
Bi-directional: Not sensitive to sounds arriving from where?
the sides
as the sampling rate increase what happens
the signal looks more like continuous time representation shown above it
what limits the amount of control we have with each aid
the size
what is the attack time
the time for monitoring circuit (compressor) to sense presence of loud signals and turn the amplifier down
compression in analog aids is where
the volume control located in circuit dictated if compression was input or output
how can programs vary
they can vary in terms of frequency response, compression characteristics, other features
closed platforms of HAs
they have an inherent set of processing rules that cannot be changed by the dispenser
adaptive dir mics are easier to use because
they may translate to better benefit and satisfaction
why was DSL important for children
they need to hear their own production of HF consonants to acquire speech
open platforms of HAs
this allows the dispenser and patient to quickly and easily access a variety of distinct signal processing algorithms
fig 6 calculated what
three categories of HL (not good for HL over 70 dB HL)
what is the release time formal definition
time is takes for the output signal to increase to within 2 dB of its final value following a decrease in input level from 90 dB to 55 dB SPL
what is the attack time formal definition
time taken for the output to stabilize to within 2 dB of its final level after the HA increases from 55-90 dB SPL
what is the ability of DSP aids which makes them easier to use
to analyze the signal and make decisions for the patient, which makes HAs easier to use
Why is Front-to-back ratio used?
to check directivity in a hearing aid to ensure functionality
What is the goal of the articulation index?
to create a "real-world' measure of directivity
what was the goal of the 1/2 gain
to get average speech 65 dB SPL inputs near expected MCL
what do polar plots default to
to hypercardiod in diffuse fields of noise
What do Through-the-ear aids claim?
to increase clarity and improve comfort
what is the goal of the wide dynamic range compression
to provide more gain for lower input signals than for higher input signals (acts as IHC)
how is DNR designed
to reduce annoyance of certain transiet sounds
negative impact of low kneepoints release results in
too many soft sounds amplified
room reverberation does what to speech
too much reverberation reduces speech intelligibility
What is the AI- Count the dots?
total of 100 dots in "speech banana"
BTE Directional Hearing Aids: where is the front mic? (expect phonak)
toward the top
what is frequency lowering affected by
transposition, compression, or shifting
Disadvantages of body aid (2)
ugly and noisy
what HL is not good for dir mics
unilateral
how do we optimize frequency lowering
use the smallest amount of frequency lowering possible to obtain largest improvement in audibility
What were BAHA's used for and what are they used for today?
used to be conductive loss but now for single sided deafness
Why do we want to weigh each band appropriately for AI?
used to determine how successful a person will be with amplification
what are multi-channel HA
uses 2 or more circuit paths
what does the clock use in the HA
uses fixed vibrations of a quartz crystal to send a steady stream of pulses to the microprocessor
for home environments what is the best solution for improving hearing in noise
using remote microphones and other ALDs
what are single channel HA
utilizes a single circuit path through which all frequencies pass -all frequencies processed together (this allows less manipulation)
with directional mics what will enhance environment performance
utilizing the best positioning - we need to counsel patients to make a beam forming mic
Higher Order Directional Mics: HAs used to connect for ________ but now what can they do?
volume; talk to each other to figure out what to amplify
If a patient does not have the dexterity or would rather control volume via app, what can we do?
we can disable the hardware
follow-up counseling with pt
we evaluate wear time, monaural vs binaural, which programs are used, which used enabled features are being used
what is aliasing
when sampling rate is not high enough and error occurs known as aliasing (visualize an image that will look rough as opposed to smooth)
how is adaptive feedback suppression activated & how do we check this
when the HA detects the presence of FB -we check it by placing our hand over HA, FB should occur and then diminish
what does the monitoring circuit of the hearing aid do
when the output approaches saturation, the monitoring circuit reduces the gain
what are we not sure of for frequency lowering
who it will work for -a dozen peer-reviewed studies on modern frequency lowering techniques, no consistency across studies
what was the second commercial DSP aid
widex, it followed with senso in 1996
Dual-Microphones: if you have a signal you want to cancel, you want to make sure what?
you have a net zero
How long do batteries last in IITC (lyric)?
~120 days
How far away do you want to be for directional microphones?
~20 feet
formulae for digital hearing instruments what are the most important 3
1. DSL-desired sensational level 2. NAL-NL1 (non-linear) 3. NAL-NL2
Gain reduced ____-____ for binaural fittings, greatest for ___inputs
2-6 Loud
what has the most dynamic range
a human ear
# of _____may be less than # of ____
bands channels
what are the bands of a hearing aid
bands are also known as handles....its how dispensers can adjust response of the hearing instrument
why does mirroring the audiogram not work for us
because of the dynamic range aka the peoples LDLs
value=
benefit/cost
The higher the AI-DI the _______(better/worse) performance in noise
better
What is a BiCROS?
bilateral routing of signal
the principles of DSP
binary code sampling quantization aliasing
daily cost of HA use, what should we explain to a patient
binaural aids costing $5000 could be you spending $2.73 a day on starbucks
in digital aids what is the mathematical calculation algorithm
both WDRC (input) and compression limiting (output) compression occurring
How is Magnetic reed switch (MRS) activated?
by teal, static or permanent magnet (found in handset of most standard telephones)
digital aids today provide what
capability to make product function linearly
Digital Noise Reduction (DNR): are most modulated based, how do we do this?
carrot passage
DNR does ____ & ____ of listening
comfort & ease
fig 6 showed us that mild HL demonstrated what
complete recruitment at high input levels
at high output levels the HA
compresses a lot, we should never reach the point where peaks are clipped
what is not simply a gain control
compression in analog aids
what two things do we use in HAs today
compression limiting and WDRC
Con's for "hearables" (1)
consumers can purchase with no professional input
how does DNR work
filtering and subtraction is used
What are the two purposes of the T-Coil?
for telephone use and assistive listening devices (neck loops and loop systems)
who was POGO introduced by
gerry mccandless 1983
what is the release time
input level falls in intensity, monitoring circuit sense change and release amplifier
what is the opposite of WDRC
input signals below the compression threshold (TK) receive reduced gain rather than maximum gain
What do you have to keep in mind with the CROS system?
insertion loss
Having two ears allows us to localize based on what two things?
intensity differences and time of arrival
random noise
intensity-frequency characteristics like speech
How does hearing loss pertain to localization?
issues with localization
what is good for binaural connectivity for user VC & multiple memory features
limited transmission range
in bergers prescription what should be slightly reduced
low frequencies
noise tends to have the most energy in the ____ _____
low frequencies
with speech programs we decrease what
low frequencies due to upward spread of masking
what should we add to enhance bass
low frequencies- this provides a richer sound quality for music
for audibility and comfort in quiet we manipulate this by
multi-channel processing...but is this better?
activation time
onset and offset time (1-2 up to 5-10 secs- this is different then attack/release time)
frequency lowering intrinsic factors to consider (5 things)
-ability to learn to interpret new sounds -cognitive ability -age of hearing loss onset -listening experience -?? (lots of questions)
day of fitting or initial follow up what do we have to do
remind pt that the hearing aid records their use and what features are being employed, can help with adjustments
what did the fig 6 article "three types of sensorineural hearing loss article" show
required gain to satisfy loudness compression
the goal of current hearing instruments
resort normal loudness growth
what did practitioners begin to recognize in the 1960s-1970s
single words in quiet don't represent performance in typical listening environments
Class D amplifiers are _________(smaller/larger) in size
smaller
the purpose of the aliasing is to prohibit the introduction of the
sound aliases
what is gain
the amount by which a hearing aid increases the intensity of an input signal aka volume
what was the focus of the 1/2 gain
the focus was speech spectrum
according to the formulae the gain overcomes the attenuation caused by the hearing loss, and helps to overcome what else
the frequency filtering effects of sensory neural hearing losses
how does the hearing aid amplify
- all inputs by the same amount (1/2 gain) -some inputs more than others (this was before digital)
what are the two classes of hearing aids
- linear hearing aids - compression hearing aids
what are the 2 things related to dynamic compression
-attack times -release times
what are compression hearing aids used for
-available in analog aids -used in digital hearing aids
for POGO what is the reduced 1/2 gain at
-250 Hz -10 dB -500 Hz -5 dB
reduces audibility for very soft sounds not of interest to user
-internally generated noise from circuitry -very low-level environment sounds
IHAFF at minimum
500 and 3000 Hz warbled tones measured
Polar Plots: HA responds to sounds from ______degrees
360
_____ gain for children at ____ input levels
More Low
For sloping and precipitous HF SNHL what should we NOT USE and why?
NAL-NL 1 Because it prescribes less HF again than DSL
for flat and reverse heating losses what should we use and why?
NAL-NL1 Because it prescribes less low frequency gain than DSL
What are "hearables"
Wireless wearable computing earpieces that perform HA tasks with additional features
phase cancellation the HA detects the signal that is leaking back to the microphone and automatically does what
cancels the signal by adding the equal but opposite in phase signal
Ear canal resonance: anything placed in the ear what happens to the resonance?
changes; typically loss pf naturally amplified sounds
what does the pinna do?
collects sound and the shape funnels the sounds to focal point
What are IITC best for? (2)
cosmetics and telephone use
Own Voice Quality: "my voice sounds like it is hollow, boomy, echoes, feeling plugged, why does this happen?"
could be occlusion or amplification occlusion
who did a study on the support of premium technology
cox
what is our basic goal for DSP aids
create a clear signal, mimic the signal, audibility, comfort
What does the Trans Ear Bone conduction hearing aid look like?
custom earmold with small vibrator embedded
how do we avoid aliasing
an anti-aliasing filter is included prior to the A/D converter
With a BTE, you can use what to couple sound to ear.
an earmold or dome
Class D amplifiers have a _________(lower/higher) battery consumption
lower
Pro's for "hearables" (2)
lower cost and less stigma
DNR has potential to lighten what
the cognitive load- mounting evidence supporting this
since the introduction of DSP aids significant consolidation in what
the hearing aid industry
what is quantization
the process of describing the amplitude (intensity) of each sample
Body aids- Disadvantages: lack of what?
true binaural hearing
Class B amplifier is capable of higher gain (about _______of type A)
twice
loudness summation: sounds are about _______as loud compared to one ear
twice
how many types of DNR schemes are there
typically 3-4 types of DNR schemes being used in HAs today
How are most t-coils placed?
Diagonally
_____was clinically used occasionally
POGO
what is the clock managed by
algorithms
The directivity index is expressed in what?
decibels (dB)
what does background noise reduce
the intelligibility of speech for everyone
further technology advances involve significant _____costs
R&D
What does "in situ" gain imply?
Unaided SPL at the HA microphone aided SPL at the TM
What is a microphone array?
a microphone or group of microphones with more than one entry port
what might a patient report if they have a short release time
"cutting in and out" "pumping action"
what might a patient report if they have a long release time
"cutting off" "mumbling" "cant understand speech"
trainable hearing aids is known as
"data" learning (ex if the pt keeps turning up the VC the HA will catch on)
DSL primary goal
(if they've been previous HA users) audibility of speech make all speech sounds audible
a second interfering voice
(interference by many voices of equal intensity-speech babble): physical characteristics of random noise
what 3 things go with input compression
1. VC situated in circuit after amplifier 2. VC affects gain and MPO, not kneepoint 3. intended for mild-moderate SNHL
what 4 things go with output compression
1. VC situated in circuit before amplifier 2. VC affects gain kneepoint not MPO 3. higher power aids 4. used for children
what three things were collected in cox premium technology study
1. change in hearing-related quality of life 2. extent of agreement with 6 positively worded statements about everyday hearing with the hearing aids 3. reported preferences between the premium- and basic feature devices from each brand
what are the 4 building blocks of hearing aid features
1. convenience, ease of use and simplicity 2. speech intelligibility noise 3. comfort in noise 4. audibility and comfort in quite
what are the 2 things we have to remember with data-logging (aka the "benefits" we have with them)
1. day of fitting or initial follow up 2. follow-up counseling
multiple programs (memory) hearing aids have
1. digital control 2. program memory (quiet situations, noisy environments, music)
what did recruitment at high input levels tell us (2 things)
1. don't need amplification for high inputs 2. as HL increases, only a small amount of amplification is needed
what were the 4 things carhart tested in his goal for maximum HA benefit using a speech method
1. effective gain (using SRT stimuli) 2. best speech discrimination (using PB-50 word lists) 3. tolerance limits (under headphones) 4. efficiency in background noise (was easy to measure)
adaptive feedback suppression with phase cancellation (3 things)
1. introduction of a signal that is 180 degrees out of phase from the FB signal 2. purpose is for transient FB 3. still must ensure good fit
the signal processing steps of the DSP
1. microphone 2. anti-aliasing filter 3. analog to digital converter (A/D convertor) 4. digital signal processor 5. digital to analog convertor (D/A convertor) 6. anti-aliasing filter 7 receiver
the 6 benefits of DSP (what two things are most important to us)
1. miniaturization 2. low power consumption 3. low internal noise 4. programmability 5. feedback suppression 6. signal processing complexity
what are 4 things that people are typically interested in with DSP
1. quiet 2. noise 3. music 4. telephone
what are the three types of noise
1. random noise 2. a second interfering voice 3. room reverberation
what other factors may affect the performance of directional mics
1. vent size 2. mic port 3. alignment 4. LF gain