final exam with review topics Flashcards
explain the carbon microphone process and how it goes from acoustic signal to an electrical signal
the acoustic signal arrives to the microphone and vibrates the diaphragm which gets compressed and when it moves inward, the carbon balls get pushed together (positive voltage flow). the sound waves goes outward and will bring the diaphragm out with the carbon balls (negative signal)
-this back and forth direction results in an electrical wave that matches the input acoustic signal
overview of a carbon microphone
sound wave → arrives at microphone → pushes on diaphragm and compresses carbon balls → creates a analog signal as the sound wave continues → creates a analog electric signal → receiver picks up the electric signal and makes it back to an acoustic wave
temporal resolution
ability for the auditory system to detect small time related changes in the acoustic stimuli over time
-our system has the ability for these rapid changes and can process in order for speech intelligibility
how do time related cues affect auditory processing
gap detection, phonemic duration, temporal ordering and suprasegmentals
gap detection
being able to detect small gaps within words or between words/sounds
-such as spoon vs. soon
phonemic duration
being able to detect sharp endings of sound words or the voiceless sounds of other words
-length of words or statements or sounds
temporal ordering
are we able to retain the order of sounds as they are presented to us or do they get mixed up
-such as boots vs. boost
suprasegmentals
such as patterns of stress, intonation and rhythm
binaural loudness summation
action potentials within the brainstem increase loudness when two ears receive auditory input signals
how does binaural loudness summation impact normal threshold? supra-thresholds?
gain of around 2-3 dB ; gain of around 5-8 dB
ingress protection (IP) rating
how a device is protected from various materials or contaminants
-various degrees for protection against solids and liquids
-can look at different rates and select one based on the need of the patient
what does a 6/8 IP rating mean?
this is the top rating device
-6 is dust tight
-8 is protection against long immersion and good for max depth within water
viscosity
how easily it flows before it is cured
-high : thick, provides resistance, provides stretch to the aperture
-medium : provides some stretch to the aperture
-low : runny, loose, flows easily without resistance
why would you want a high viscosity material?
provides for the stretching of the aperture
-snugger fit
shore value
if it has the ability to remain its shape or if it will be altered after its cured
-silicone has high
-MM has low
why would you want a high shore value?
with lower values, there is a higher change for it to become damaged in the shipping process so with a higher shore value it ensure it is shipped without damage
stress relaxation
materials ability to return to its shape after removal from the ear
-high can be pulled out and will go back to its shape
-low will not bounce back
-silicone is superior and MM is inferior as the shape can be distorted
contraction ratio
shrinkage over a 7 day period, will the impression be the same in a few days or will it be altered
-silicone does not shrink, MM will shrink
occlusion effect
a common complaint when low frequency threshold loss is better than 50 dB HL
-voices can sound boomy, hollow or as if they are in a barrel
-insufficient venting or insufficient canal length can cause it
how does OE occur within the low frequencies
the skull transduces the low frequencies generated by the voice
-bone conduction signal becomes trapped within the canal
how to reduce the OE
venting and by extending the canal length
how can venting reduce OE
can release the lows out of the canal
-vocalized sounds that cause the OE are within the low frequencies so with venting it can release these frequencies
how can extending the canal length reduce the OE
by extending the canal length (canal portion of the mold) into the bony portion, the waves bouncing around are not able to make it to the cartilage therefore they cannot vibrate within the canal and the OE will not occur
-the waves will be bouncing around within the bony portion so this blocks off the cartilage portion and can reduce the OE
how does vent size impact high frequency output
increasing the vent size causes less high frequency output we get from the HA
occluding molds allow fro around ______ dB of gain
40
-supports audibility to around 80 dB HL
3 mm vent allows for around _____ dB HL of gain
30
-supports audibility to around 60 dB HL
open domes allow for around ______ dB HL of gain
25
-supports audibility to around 50 dB HL
front end distortion
occurs when the collected/incoming signal exceeds the microphones dynamic range
-complaints are due to loud music or to the users own voice
-planned for acoustical effects or unplanned
why do digital HA’s have a lower microphone dynamic range
due to using analog to digital converters (ADCs) which use a 16-bit converters allowing for a 96 dB dynamic range
-can lead to peak clipping
peak clipping
flattening out of the top of the sound wave, resulting in multiple points being stimulated in one area on the basilar membrane
-causes distortion
how is front end distortion managed within digital HA’s
they have the ability to shift their dynamic range to fit the listening situation
-when you raise the louder end, you raise the quieter end
-in loud environments it will shift upwards and you will get less within the quiet range
signal to noise ratio (SNR)
difference in volume level between the desired signal and the undesired signal
-normal hearing listeners require and ideal SNR of 2 dB (meaning speech is 2 dB louder than the noise)
-signal minus the noise
what is a null
point of maximum attenuation
-the microphone turns off
bi-directional polar plot
collection from the front and back, attenuation from 90 and 270
-used in specific situations
carotid polar plot
collecting sounds from the front and attenuating from the back
-null at 180
-DI of 4.8 dB SNR
super carotid polar plot
collecting from the front and back, attenuates at the sides (125)
-DI of 5.7 dB SNR
hyper carotid polar plot
collecting from front and back, attenuation from sides (110)
-DI of 6 dB SNR
what is the TK (threshold kneepoint)
the point of activation for the compressor to begin working
-signal for the compressor to alter or begin
shifting the TK down (smaller) causes the output to ______ for soft sounds
increase
shifting the TK up (bigger) causes the output to ________ of soft sounds
decrease
how can we either raise or lower the TK within a practical setting
if a patient can hear and perceive soft sounds as being soft, lowering would be beneficial whereas if a patient cannot hear perceive the soft sounds as anything besides noise increasing the TK may be beneficial
expansion
rapidly adds gain to very soft input signals until the first TK, which lowers output of those signals
-CRs lower than 1:1
-manages intensity of very soft input signals and circuit noise
analog to digital conversion (ADC)
chops sine waves into bits and assigns numbers to it
-taking the electrical signal and putting it into a digital word which is a series of 0s and 1s
what does ADC require in order to occur
sampling rates and quantization
sampling rates
they measure spaced moments of time along the electrical signal and DSP only uses these samples points and the other parts of the signal is ignored
-each cycle of the wave must be represented by at least two sampling points
quantization
bit resolution
-this rounds each sample and creates a digitized version of the signals that results in a less idealized representation of the analog input signal
digital to analog converter (DAC)
takes the digitized signal and transduces it back to an electrical signal
-digital to analog electrical signal that goes directly to the receiver
processing speed and DAC
the time it takes for it to occur can impact the quality of the sound
-can sound like an echo
what occurs as a result of quantization errors
can create soft random noise within the HA referred to as the noise floor
explain how an overlap exists between auditory filters
high frequency bands pick up lower frequency signals from adjacent critical bands
-as a result, noise masks signals within the adjacent critical band
what is the effect of low frequency masking to a damaged cochlea
the critical bands within the cochlea are organized by frequencies and so what occurs is one frequency range spills into another range, which is the upward spread of masking
-a 250 Hz noise can impact noise all the way up to around 1500 Hz
-meaning you have to manage noise under 1500 Hz to help manage the noise present
how is sound cleaning achieved within the spatial domain
through the usage of directional microphones
-automatic microphone switching (adaptive) and adaptive directional mics (null steering)
automatic microphone switching (adaptive)
automatically changing from omnidirectional to directional mic in the presence of background noise
-can be fixed directional or adaptive directional
-helps aid reduction of background noise
-occurs automatically and continuously, reverting back to omnidirectional in quiet
-there is a override switch that can be activated for the patient
fixed directional
one polar plot and is superior in the presence of multiple noise sources
-mic switches from omni to fixed with one set of polar plots, no steering of the null
adaptive directional
multiple polar plots and is superior when only a few noise sources are present
-not effective with higher sources
-includes steering of null
beamforming mics
very narrow directionality that makes decision based on how loud the room is
-bandwidth narrows as the environment intensity increases
-works well for improving speech intelligibility
how is sound cleaning achieved within the temporal domain
digital noise reduction
digital noise reduction (DNR)
reduces steady state noise over long periods of time
-lowers the output of signals with fast modulation rates and low modulation depths
-it varies on signal intensity or program settings made during the fitting
DNR can improve …..
listening comfort by reducing listening effort and cognitive load
DNR cannot improve …..
speech intelligibility
modulation rate
how quickly the signal is fluctuating
-speech is slow and noise is fast
modulation depth
amplitude variations between the loudest and quietest portions of the signal
-speech is high (variable) and noise is low (not variable)
how is poor SNR determined in a HA
if there is noise in speech and the amplitude of the speech is not much different than the amplitude of noise that is detected as a low SNR HOWEVER is the speech peaks of speech has a greater modulation depth the HA can detect that as a good SNR
how is sound cleaning achieved within the spectral domain (frequency)
reduction of the output within the low frequencies occur due to majority of our understanding of speech comes from the mid and high frequency signals
-high frequency noise competition remains present even though low frequencies are less audible
weiner filter function
spectral subtraction approach
-speech signal and noise are present and when there is a pause, there is the ability to measure noise
-measures short term noise spectrum during gaps within the speech
-records MR and MD and subtracts it from the overall signal
the weiner filter improves __________ but does not improve __________
acceptance of background noise ; intelligibility
what are 3 methods used to reduce external feedback
reducing external feedback loop, digital notch filtering and digital feedback cancellation
reducing external feedback loop
increasing the snugness of the mold to reduce the size of slit leaks, which will increase the occlusion effect
-so then you decrease vent size to stop the occlusion effect feedback path
digital notch filtering
occurs through creating a notch within the 2-4 kHz range
-works by removing a narrow band of frequencies around the feedback
-reduces gain in this range until feedback stops
-this is the range of speech and it will stop audibility for soft signals
digital feedback cancellation
the HA will start to feedback and a duplication is made of that signal which creates an out of phase wave which cancels out with the feedback wave
-can attenuate or distort parts of the speech signal
frequency lowering function
attempting to improve HF audibility by shifting them to a lower frequency, attempting to improve ability to understand
what are unintended consequences of frequency lowering
adding distortion and can drain battery
what are the 3 ways frequency lowering occurs
linear frequency transposition, nonlinear frequency compression and spectral envelope warping
linear frequency transposition
this is a cut and paste approach in which a HF band is moved and octave down to a lower frequency region
-HF signal is cut out and is shifted to a lower octave
-there is an adaptation period that needs to occur as these HF signals are now mixed in with the low frequencies
nonlinear frequency compression
a range of high frequencies is compressed into a lower frequency range
-takes inaudible HF and compresses them into a LF region that is audible
-tonotopic order is remained however it will sound distorted but without this they would not be able to hear these signals despite the level of amplification
spectral envelope warping
this is a copy and paste approach in which high frequency signals are transported into a lower frequency band but that HF band remains in place
-gives the patient two chances for detection
what are some digital wind noise reduction methods
low frequency filtering, audio signal from least affected microphone is streamed to the affected side and a directional microphone may be switched to omni mode within the LF channel
what are benefits of binaural processing technology
volume control synchronization, program changing synchronization, bilateral output for telephone signal, bilateral wind noise management and single microphone directionality in a CIC
with binaural processing, we need to think about WDRC explain why this is
due to a head shadow, as the sound goes from the source side to the other side it will decrease causing WDRC to activate and add gain to the non-source side to amplify the soft signal, leading it ILD’s decreasing and directionality to be lost
-HOWEVER, with the ability of the HA’s talking to each other the talking from the source side to the other side can occur to inform for not adding as much gain to the soft signal so WDRC is erased and is no longer occurring which results in the interaural level differences remaining and directionality remaining possible
what is the purpose of the acoustic chamber
designed to reduce reflection
-it is calibrated
reference microphone
calibrates the SPL output from the test box speakers
-monitors signal intensity and automatically adjusts speaker volume to maintain appropriate intensity
coupler microphone
measurement microphone sealed into the coupler that collects the output data from the HA
-measuring the sound that comes through the HA and measuring the amplified output of the HA
HA-1 coupler
stimulates the size of canals with custom products
-devices are attached using fun tak (putty)
HA-2 coupler
long stem mimics the tubing that travels from the ear hook down to the canal
-used for BTE devices
prior to running an ANSI measurement, ensure to turn the device to _________
test mode setting
why is an ANSI measurement useful?
tells us if the device matches the specification sheet and informs us on the functionality of the device
-if it has enough volume/capacity to meet the patients needs
OSPL90 (output SSPL @ 90)
test box puts a 90 dB into the HA to find out how loud the MPO is coming out of the HA
-identifies the loudest possible output point the device can produce for a 90 dB input signal
HFA OSPL90 (high frequency average output SPL @ 90)
averaging 3 frequencies and saying what the average is for the MPO
-MPO at an average of the 1000, 1600 and 2500 Hz
HFA FOG (high frequency average full on gain)
intensity drops down with it being presented to the HA
-tells us the available gain
equivalent input noise (EIN)
measures the internal noise of the HA
-should be no louder than 30 dB
total harmonic distortion (THD)
measurement of signal distortion
-marked as a percentage
-determine if the output signal contains harmonic frequencies that were not present in the input signal
frequency response
frequency limits of the bandwidth
-useable bandwidth of device that claim HF output
how to run an ANSI measurement
place within the box, select ANSI, run test and when set VC to RTS appears readjust until the green triangle is close to the 0 line
when testing directional microphone, what does the heavy line represent? the light line?
heavy represents the output from the front microphone and the light represents output from the back mic
-they show the ability for it to be attenuated
telecoil magnetic field simulator (TMFS)
checking to see if the telecoil is functioning the way the manufacturer says it is
-holding the HA flat and moving around the T to find the highest field
sound pressure level for an inductive simulator (SPLITS) measurment
output of the TMFS signal in which the telecoil transduces the input signal from analog signal
relative simulated equivalent telephone sensitivity (RSETS)
taking the output associated with the microphone and we subtract it from the output associated with the telecoil to get a value
-positive is the telecoil output is louder than the microphone output
-negative is the telecoil output is softer than the microphone output
how do input stage variables impact the output of the device
changes the sensitivity in the microphone to broad frequency range
how do processing stage variables impact the output of the device
converts sampling rate determines the highest frequency the device can produce
-this is the first limitation of the frequency response of the HA
-A/D converter limits the intensity of front end input
how do output stage variables impact the output of the device
receiver size and design along with the sound bore
-signal will change as it moves through the sound bored
receiver function
transduces the amplified electrical signal back to an acoustic signal
-larger receivers produce a higher output
how do receivers function
flexible strip of metal called the armature is balanced between two magnets like a diving board
-top and bottom magnet each relating to a positive or negative direction
-as the electrical current flows through the coil, the armature is magnetized and pulled towards one magnet or the other
-the armature is connected to the diaphragm and its movement pushes and pulls the air creating an acoustic signal
a larger receiver is needed for severe losses leading to limitations in output bandwidth, how are these designed to eliminate this limitation
two receiver system (doubles the size)
-output from both receivers is summed before reaching the TM
-this extends HF bandwidth with little compromise on the low frequency
-reduces battery drain
-minimizes potential saturation
what are common receiver limitations
saturation, shock damage, moisture and debris
saturation
occurs when the output exceeds its capabilities
-amplified signal is peak clipped
-amplifier will drive the receiver with a higher voltage (battery drain)
-HA has exceeded its capacity, square wave output similar to peak clipping
shock damage
any vibration is going to vibrate the HA which will get back to the HA which turns into a noisy sound
-vibration of dislodged receiver radiates back to the mic adding extra frequencies to input signals
sound bore path
the column of air a sound wave passes through as it leaves the receiver and arrives at the TM
-from the receiver to the canal
the final output changes based on the ___________
sound bore path
what frequency range is impacted by changes to the sound bore
generally higher frequencies
how are standing waves observed within the sound bore
reflection within the sound bore cause the wave to overlap with itself resulting in standing wave resonance
-as soon as it leaves the receiver, it is traveling through different material which can create standing waves
how do thin tubes impact the output
they attenuate the HF signals
-less output in the highs because the diameter goes smaller
-when you attenuate these HFs, you may also be taking the primary resonant peak and shifting it down to a lower frequency
how do libby horns impact the output
increasing high frequency output
-intensity of the sound arrives to a narrower spot and is expanding, which causes the signal to have HF output added
-benefit is dependent on maintaining the length of the flared end
damper
smooths resonances in the final frequency response
-type of acoustic resistor designed to make sound attenuate slightly as it goes through
-able to smooth peaks
-can get clogged as they are a type of screen door
what type of device are damper’s typically seen in
BTE’s
-varying placements however most common is the middle of the ear hook or at the end of the ear hook
lithium ion batteries
rechargeable battery that is becoming more popular
advantages of lithium ion batteries
energy efficient, significantly longer battery life, fast charging mode and lasts the life of the HA without removal or change
disadvantages of lithium ion batteries
faulty battery chargers, no replacement alternative if battery loses charge, must replace every 3-4 years, and option available mostly within higher end devices
zinc batteries
peeling off the top to expose air hole which allows for oxygen to flow inward and interact with the zin that creates the + and - flow
-once activated, a battery can hold charge for around 6 weeks
how to maximize battery life
store in a secure location, avoid extreme moisture, don’t store batteries with other ones as this can cause contact discharge, let battery breathe before usage, monitor streaming use which impacts battery life
advantages of zinc batteries
convenient, can get smaller HA’s and reliability as it it typically easy to fix
disadvantages of zinc batteries
smaller battery space (poor option for individuals with dexterity issues)
factors that can reduce battery life
wireless transmission, FM signal processing, tinnitus masking programs, bluetooth streaming features and low battery warnings
SOAP notes
subjective (patient history), objective (diagnostic testing), assessment (linking together history and results, what could it be), plan (management recommendations)
advantages of SOAP notes
organizes thinking, facilitates inter-professional coordinated care
-expected structure within the medical community
SBAR notes
situation (brief statement of problem), background (follow up with case details), assessment (statement of concern), recommendation/request (what are you asking of them)
patient centered care (PCC)
active involvement of patients and their families in the design of new care models and in decision making about options for treatment
fiduciary
involving trust and how it is place with confidence on another to exercise discretion or expertise in acting on behalf of the client
how does fiduciary relate to PCC
you want to ensure there are direct conversations to probe and reveal the desired outcomes
-spend time listening to the patient history and needs
-provide them with options without overwhelming the patient
what does reimbursement do
provides revenue to practice, pays operating expenses, pays salaries, supports negotiations for wage increases
what are medicare’s physician order requirements
a physician order is required for all audiology serves
-patient needs to talk to their doctor about their hearing and get an order to be tested then can come and get testing
what are some examples of what medicare will reimburse for
evaluation of the cause of disorders of hearing, evaluation of suspected change in hearing, determination of the effect of medication, reevaluation to follow up regarding changes in hearing, failure of a screening test, diagnostic analysis of CI or audiologic diagnostic test before implantation
what are some things medicare will not reimburse for
screening evaluation and if they are going through treatment with no improvement
under what condition will medicare not cover a diagnostic assessment
if there is no medical necessity
-there needs to be a reason for it to occur
-if a patient comes in with concerns regarding hearing only, you cannot do a vestibular test
CPT-4 codes
describing the primarily diagnostic procedure
-stronger codes
HCPCS codes
describing the services and supplies that are not defined or outlined within the CPT-4 coding system
-codes for services that we provide and services as they relate to amplification and repairing amplification
ICD-10 codes
classifying the diagnosis or symptoms
-selection must support the services your provided
