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Hearing Aids Midterm
Terms in this set (158)
When during the appointment are RECDs measured?
before placing hearing aid with probe mic in ear for REM
How far from the eardrum should the probe mic be?
The end of the probe mic should be how many mm past the end of the hearing aid/dome in the eardrum? Why?
If not far enough in, can cause resonances to appear that don't actually exist
6 methods for probe tube placement
visually assisted: using otoscope
acoustically assisted: using REUG
geometric: measure earmold/dome and add 5 mm
bump and pull
audioscan probe guide
Shallow probe tube placement during REM affects (high/low) frequencies the most.
DSL fitting formula uses loudness (equalization/normalization). What is this?
goal: amplify speech sounds so normal inter-frequency loudness relations are maintained
soft speech sounds soft and loud sounds loud; optimizes audibility (generally louder)
low frequency vowels get more loudness weight than high frequency consonants (because that's normal)
NAL fitting formula uses loudness (equalization/normalization). What is this?
goal: amplify speech sounds so they're perceived as equally loud; results in higher speech intelligibility
aims to normalize perception of overall loudness
NAL optimizes (audibility/speech intelligibility), while DSL optimizes (audibility/speech intelligibility).
NAL: speech intelligibility
How far should a patient be from the Verifit speaker during REM?
What is the purpose of the equalization tone (static) played by the Verifit before the carrot passage?
compensates for the distance the patient is from the Verifit
controls SPL as a function of frequency
What is the LTASS?
long term average speech spectrum (line inside green shaded area)
shaded area shows maximum and minimum values
T/F: The opposite hearing aid does not need to be muted when running MPO.
false- should mute so you know which ear patient is responding to
2 patients with the same audiogram may not actually hear the same. Why?
acoustics of individual's ear canal can change level of tone at eardrum
What is REDD?
real ear dial difference
difference between intensity setting in HL on audiometer dial and the output in the ear canal
REDD = RETSPL + RECD
What is RECD?
real ear to coupler difference
difference between the dB SPL output of a signal in a 2-cc coupler and the ear canal
What is RETSPL?
reference equivalent threshold in SPL
difference between HL and the output of a 2-cc coupler
How does the Verifit convert dB HL to dB SPL?
It automatically uses an average REDD
also uses average RECD if values aren't measured
clinical purpose of 2 cc coupler
allow real-ear verification for people who can't sit through it (infants, kids, difficult to test adults)
The volume of an ear canal with an insert earphone/earmold in place is usually (smaller/larger) than the volume of a 2 cc coupler.
RECD values are usually (positive/negative).
positive- because output of true ear canal is greater than output of coupler (since EC volume is usually smaller)
The smaller the ear canal, the (smaller/larger) the RECD.
RECD coupling should match....
hearing test coupling
How can a shallow probe tube affect RECDs?
results in negative high frequency RECDs
How can a crimped, pinched, or blocked probe tube affect RECDs?
results in significant negative RECD values across spectrum
How can a PE tube or perforation affect RECDs?
results in negative low frequencies
bigger perforation --> larger effect
What is WRECD?
wideband real ear to coupler difference
used by Verifit 2 to reflect expanded bandwidth of modern HAs
What do RECDs assume about venting?
assume little to no venting
When/why is S-REM an inaccurate fit even with perfectly measured RECDs?
can't take venting effects into account
Why aren't RECDs standard for adults?
less likely to do S-REM with adults
adults' ears don't vary as much compared to the 2 cc coupler
What is the primary purpose of measuring RECDs?
When should you not use RECDs?
when thresholds were measured with TDHs or in soundfield
S-REM with very open fitting
What purpose do RECDs serve for live REM?
takes into account the ear canal size, which changes thresholds and therefore targets
T/F: Open fittings cannot be completed in the testbox.
true- even with RECDs
In general, you want to stay within ____ dB of targets for REM.
Why might NAL targets be below a person's thresholds?
desensitization: sometimes making sound louder hurts overall discrimination (causes distortion)
What are some examples of when you may deviate from targets during REM?
patient can't adjust to sound with HAs (sound sensitivity)
many targets below patient's thresholds
patient accustomed to a less accurate fitting and can't adjust (wants more power or amplification in certain regions, etc.)
When should you repeat REM after an initial fitting?
significant changes in acoustic coupling (closed to open)
change in hearing
unable to resolve patient complaint
When might you fit a HA without REM?
extremely stenotic or collapsed canals
IIC or Lyric that doesn't have room for probe tube
BUT do S-REM if possible
What testbox measure can serve as a cross check for a listening check?
S-REM- can detect things our ears can't
What is in situ audiometry?
play tones through manufacturer software and patient responds, generates basic audiogram
According to research, how do in situ audiograms tend to compare with traditional booth audiograms?
overestimate low frequencies, underestimate 4 k
results more comparable with more hearing loss (because coupling is more closed)
What are some common things that can limit the gain of HAs?
T/F: The availability of Bluetooth in HAs drastically improved speech understanding in users.
false- only for phone calls
What is the oldest form of wireless streaming from HAs?
How many different regions is the world divided into for radio frequency transmission? Why is this necessary?
radio waves not an unlimited source
Which radio bands are used for hearing aids?
ISM radio bands
T/F: NFMI is capable of carrying audio and data signals.
NFMI pros and cons
pros: very low energy, goes through/around objects (head) easily
cons: decreases within a meter, can have interference with other types of magnetic sources, can't receive outside audio source (phone) due to short range
What frequency range is typically used for Bluetooth?
pros and cons of 2.4 GHz transmission
pros: farther distance than NFMI
cons: uses more power, doesn't go through objects (head) easily, 2.4 GHz getting crowded
900 MHz radio frequency transmission
far field AND near field transmission
cross between 2.4 GHz and NFMI
used by Starkey until 2018
T/F: 2.4 GHz is just a type of Bluetooth.
Why did so many HA manufacturers partner with Apple first?
Apple didn't change as much over time, could give manufacturer's more consistent proprietary Bluetooth
How many HAs would a patient have to wear at once to transmit as much energy as their phone does when held up to their ear?
What technological advancement in HAs allowed for remote fine tuning?
When might remote fine tuning be a good thing? When not?
good: pandemic, remote communities
bad: requires person comfortable with smartphone, can remove chance for REM
Why is MedEl not a proponent of bimodal communication?
ties you to a single HA brand for the life of the implant
companies don't update these HAs as quickly as other models
no real practical benefit
What is the main purpose of directional microphones?
Which couplers are used for directional mic testing?
silver coupler (Verifit 1 and 2)
For Verifit 1, how is the HA positioned for directional mic testing?
front mic facing left speaker, back mic facing right speaker (even if custom has to be upside down)
placed on top of X
In a directional mic test, what do the dashed and solid lines represent?
dashed: rear mic
solid: front mic
At what level do most hearing aids switch into directional mode?
70 or 75 dB
Why is it important to have a separate directional mic test?
only testing in test box will tell you if they're providing an SNR benefit
very hard to hear DM problems in listening check
EAA and REM won't detect problem between mics
T/F: The separation between directional mics can lessen over time.
true- electronic components of HA shift out of place
It is valuable to retest EAA and DM every ___ years.
Why might there be little to no separation between the 2 lines in some frequencies during directional mic testing?
little to no separation may mean there's no amplification in that region (sloping HL)
For which testbox measurement do you have to run EAA first? Why?
It uses a value from EAA for telecoil measures.
Telecoils in the (horizontal/vertical) position are better for loops, and those in the (horizontal/vertical) position are better for phones.
What is the TMFS in the testbox?
telephone magnetic field simulator
coil placed under test surface intended to simulate telephone handset
What is SPLITS?
SPL in a horizontal magnetic field
replicating a telephone system
What is HFA-SPLITS/HFA-SPLIV?
average of the SPLITS/SPLIV curves at HFA frequencies
What is the RSETS?
relative simulated equivalent telephone sensitivity
HFA SPLITS minus (RTG+60)
What do positive and negative RSETS/RTLS values indicate?
positive: greater output with telecoil than mic
negative: greater output with mic than telecoil
What is SPLIV?
SPL in a vertical magnetic field
replicating a loop system
What is RTLS?
relative test loop sensitivity
output of HA in telecoil vs regular mode
Does the Verifit 1 or 2 require a tele-test handset? How can this be used?
can be used for on-ear testing
During telecoil testing, custom HAs are placed with the faceplate (up/down).
What can you do if the output of the telecoil program is way off from targets?
program using REM (only with Verifit 2)
done by holding tele-test handset against hearing aid like a cellphone
When measuring distortion in the testbox, the numbers should be below ____%.
5%, but ok to accept below 10% for old HAs
For (distortion/telecoil) testing in the testbox, the hearing aid is left in user settings and does not need to be connected to manufacturer software.
Why is battery drain not tested more often in clinic?
battery pill doesn't always fit into HAs battery doors
can't test rechargeable batteries
What are some pros to conducting more testbox testing?
less frustration/greater patient satisfaction
less time fine tuning defective HAs
lower return for credit rates
What are some examples of digital signal processing in HAs?
What is the overall goal of noise reduction?
improve SNR to improve speech understanding
Why can't HAs work as well as noise cancelling headphones?
HA never seen known, independent versions of speech and noise
for headphones separation between speech and noise is very clear
Why is noise reduction such an issue with open fittings?
can only cancel noise in the areas where gain is provided (likely high frequencies)
What is the one feature of HAs that improves SNR?
T/F: Noise reduction features help improve speech intelligibility.
false- sometimes even harm it (only help with listening comfort)
What are the stages of digital noise reduction?
signal detection and analysis
application of gain reduction
What is one major difference between speech and noise?
Speech has fewer modulations with greater depth than noise.
same modulation rate across various channels (frequencies)
Speech modulates at what rate?
T/F: Speech is more predictable than other types of sounds/noises.
true- human vocal cords resonate in a limited way
How can HAs use modulation depth to separate speech from noise?
Analyze modulation depth and estimate SNR in that channel
speech modulated with more depth than noise
What is the modulation depth of clean speech?
What are some common noise reduction strategies?
decrease low frequency gain or raise kneepoint for compression
How does Weiner filtering work to reduce noise?
alter gain at each frequency depending on the SNR in that given channel
gain is reduced as SNR worsens
alter gain in channels with poorest SNR and leave other channels alone
How does spectral subtraction work to reduce noise?
magnitude of noise spectrum subtracted from magnitude of speech spectrum
broad-spectrum reduction across many frequencies
most useful for unchanging noise
What can/can't you promise patients in terms of noise reduction features?
does not improve speech intelligibility in noise
does not degrade sound quality in noise
reduction applied to noise likely also removes some of speech signal
What is the general process for verifying noise reduction in the testbox?
run test at 70 dB with noise reduction off
repeat with noise reduction on
stimulate for at least 10-15 secs before stopping curves
How does wind noise physically affect HAs?
wind blows over mic ports, generates turbulence and displaces mic diaphragms
How do HAs determine if noise is wind or not?
looks at correlation coefficient (how random sound is) to determine if it's wind (which is very random)
What modern HA features can actually make wind noise worse?
directional mics: more sensitive to near field sounds than omni, can be amplified up to 20 dB
wide dynamic range compression: amplifies soft sounds
What programming adjustments can be made to help with wind noise?
decrease low frequency gain
split directionality (omni in low frequencies and directional in high)
omnidirectional (if can't do split)
decrease gain for soft inputs
increase noise reduction
consider lowering MPO
What physical adjustments can be made to help with wind noise?
add wind screens to mic ports
relocate mic to helix
face the wind
cover HA with sleeve/shield (EarGear)
What are the 3 types of feedback and which is most common?
acoustic: most common
mechanical: physical vibration of something rattling
electromagnetic: only occurs in telecoil program
Acoustic feedback usually occurs at what frequencies?
What modifications can be made to help with acoustic feedback?
more closed fitting
remake EM/change style
greater distance between receiver and mic (BTE vs CIC)
reduced gain in high frequencies
higher level technology
What are some causes of acoustic feedback?
EC shape, jaw movement, ear wax, shallow insertion
style, venting, tubing, canal length
talking, chewing, hugs
earmold tube leaks, cracks in casing
What are the 3 main DSP approaches to managing feedback?
adaptive gain reduction
adaptive notch filtering
phase/feedback path cancellation
How does adaptive gain reduction work to manage feedback?
reduces gain if feedback is detected within a channel (sometimes for all input levels but usually just soft)
kicks in only when feedback is detected
How does adaptive notch filtering work to manage feedback?
when feedback is detected, sharp notch filters are generated at feedback frequencies to suppress it
some HAs can create multiple notches, others only one at a time
basically reduces gain in a targeted region
How does phase/feedback path cancellation work to manage feedback?
generates signal opposite in phase of feedback to cancel it out
Why can it be beneficial to check for feedback using the Verifit?
can pinpoint exact frequency of feedback and only manipulate gain there
take high frequency content and move to a lower frequency region where it can be made audible
better access without using loudness
What are the 3 methods of frequency lowering?
frequency transposition (spectral envelope warping)
linear frequency transposition
non-linear frequency compression
only used by Starkey
moves sound to a lower frequency range but also keeps original sound energy where it was
linear frequency transposition
deletes high frequency energy altogether and moves it to a lower frequency region
non-linear frequency compression
most common strategy
"smushes" sound into a tighter region
can make sound seem more unnatural
Frequency lowering is more commonly used for (children/adults).
In the past, AuDs testing hearing and wrote a prescription for HAs that was taken to ______.
hearing aid dealers
Why was ASHA initially opposed to AuDs selling HAs? What changed this and when?
concerned AuDs would lose credibility as health providers if they sold a product
Supreme Court ruling about engineering saying professional organization can't limit livelihood/making profit
T/F: Education for AuDs and hearing aid dealers has increased over the years.
false- increased for AuDs not HADs
What really separates AuDs from HADs?
aural rehab and counseling
really just best practices
Why is there so much variability in how much people like their HAs?
lots of variability in where hearing aids are bought and programmed (or not)
What are the big 5 HA companies?
WS Audiology: Widex, Signia
Sonova: Phonak, Unitron
GN: Resound, Beltone
Starkey: Starkey, Audibel
What is one way insurance companies have started covering more HAs? What's a problem with this?
partner with 3rd party programs/administrators (TPAs) and only cover from those clinics
very poor reimbursement for AuDs
T/F: OTC hearing aids are regulated by the FDA.
false- regulation should be coming soon
What are some tradeoffs of Costco hearing aids?
usually fit by HADs, don't often do REM
not suited to treat complex medical needs
some HAs locked
some features removed from HAs
Who are the top 2 sellers in HAs in the US?
What is the problem with the 2019 Consumer Report showing that Costco/Kirkland Signature was the top HA?
don't ask about provider
Kirkland aids rotate manufacturers- really shows average of various manufacturers
rose to top for value
What was a notable trend in the 2019 Consumer Report about HAs?
top brands most likely to be fit by AuDs, bottom more likely to be fit by HADs
On average, it takes people ___ years between when they are aware of HL and when they get tested.
According to Marketrack research, satisfaction of HA users is higher than PSAP users in all categories except ____.
factors contributing to HA cost
supply and demand
bulk price given to select markets (VA, Costco)
only 5 major manufacturers (little competition)
research and development
device and services entirely out of pocket for patients
What did the 2017 OTC hearing aid act do?
required FDA to create new category of HA in order to help cost barriers
August 2020 deadline for regulation, pushed because of COVID
but summer 2021 executive order giving new 120 day deadline
What changes were proposed to Medicare in 2019?
classify AuDs as providers (currently diagnosticians)- would allow to bill for more services
What are some goals for OTC HAs?
increase access, make HAs direct to consumer
more options- more competition
devices preset with "average" HL or self-programmable
What are some (supposed) restrictions on PSAPs?
not for children (under 18)
not FDA approved for treatment of HL
for mild-moderate HL
PSAPs might be appropriate for what types of patients?
borderline HA candidates
difficulty in only select environments
high risk of device loss damage (cognition concerns)
What are some popular PSAPs?
Etymotic: The Bean
Sound World Solutions: CS-50
In general, how does music compare to speech?
taller crest factor
wider bandwidth of frequencies
T/F: Many DSP features (feedback/noise reduction) are helpful in improving the quality of music.
false- distorts quality
What specifically causes distortion when listening to music through HAs?
aliasing- high frequencies in music are higher than half the sampling rate are aliased down to lower frequencies
input exceeds DR of HA --> peak clipping or compression
A ____ bit system is most common in HAs. This is equal to a max ___ dB DR.
What is a crest factor? What is the average crest factor for speech vs music?
1/2 of peak
speech: 12 dB
music: 18 dB
What do most HAs do to help with music quality?
at 95 dB+, input compression before A/D conversion to avoid clipping signal
What modifications can be made to improve music quality?
turn off auto features (feedback management, frequency lowering)
omni directional mics
decrease overall gain and MPO
trick HA into thinking input is lower (turn down stereo and turn up HAs, tape over mics)
fit HA with REM as normal
probe mic in better ear
sound directed from 45 degrees from better ear side with devices on, compare to original run
sound directed from 45 degrees from poorer ear side, CROS mode on Verifit (measures response in better ear w reference mic live in poorer ear)
all 3 responses should match up
last one: measure from front, all lines should be on top of one another
T/F: HA and CROS responses on the Verifit should be the same.
true- transparent transmission of sound
Why is the battery life shorter for a CROS than for a HA?
transmitting signal takes more battery- like 12-13 hours of streaming
Do prescriptive targets change based on the type of HL? Why?
yes- but ABG accounted for differently depending on fitting formula
CHL can tolerate more gain before there's cochlear distortion
NAL-1/2 vs DSL approaches to ABG
NAL: 1/2 BC +3/4 ABG
DSL: less of a difference but still provides more gain for CHL
What are some special considerations for CHL?
choose HA that can handle additional gain with CHL
drainage or infection? maybe need more open fit
may program before, during, and after tx
What are some common complaints of people with precipitously sloping HL?
poor speech discrim
feedback with HAs
What are some common complaints of people with a reverse slope HL?
hard to understand speech on phones
understand women/children better than men
In what case may fitting to targets yield not optimal results? Why?
reverse slope HL
possible low f dead regions
upwards spread of masking
What are some considerations for fitting reverse slope HL?
leave fitting as open as possible
consider underfitting low f's (upwards spread of masking)
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