Final Exam Flashcards
(100 cards)
1
Q
goal of prescriptive formulas
A
- achieve amplification settings that are appropriate for the patient
- objective:
- –generate a target for gain or output as a function of frequency and intensity
- with the prescriptive approach , anyone can replicate your recommendation anywhere
2
Q
two times prescriptive formulas can be used
A
- during selection
* during verification of hearing aid output
3
Q
considerations for choosing a fitting strategy
A
- amount of audiometric and related information
- availability of age-specific corrections
- flexibility in selection of transducer type
- resulting targets:
- –REIG
- –REAR
- –OSPL90
- –coupler gain
- –output in the coupler
- –other HA parameters
4
Q
how are targets for HAs devised?
A
- computer-based fitting software
- –stand-alone computer programs
- –software programs provided by manufacturer
- –formulae included in real-ear gain analyzers
5
Q
how are fitting strategies and prescriptive formulas characterized?
A
- type of gain application
- –linear or nonlinear gain application
- amount and type of audiometric information required
- –only thresholds, loudness scaling data, or both
- underlying theoretical rationale
- –loudness normalization
- –loudness equalization
6
Q
linear prescriptive formulas
A
- only prescribes 1 target per frequency
* targets are used to amplify conversational speech and bring it to the level of the listener’s MCL
7
Q
compression based prescriptive formulas
A
- provides more than 1 target per frequency
* establishes ideal gain targets for various intensity inputs
8
Q
two different types of formulas that require two different types of audio info
A
- threshold-based formulas
- –pure tone audio only
- loudness based formulas
- –audio thresholds plus measured MCL, UCL, and/or loudness scale data
9
Q
what are the two underlying theoretical rationales for prescriptive formulas?
A
- loudness normalization
* loudness equalization
10
Q
what is the goal and assumption behind loudness normalization
A
- Goals: restore normal loudness across the frequency bands
* based on the assumption that restoration of normal loudness perception will lead to greater acceptance by the user
11
Q
what is the goal and assumption behind loudness equalization
A
- goal: achieve equal loudness across frequency bands
* patient perceives all frequency bands with equal loudness
12
Q
what are the 5 linear formulas for loudness equalization
A
- Half-gain rule
- berger
- POGO
- NAL-R
- libby 1/3
13
Q
what are the 2 nonlinear formulas for loudness equalization
A
- NAL-NL1; NAL-NL2
* DSL
14
Q
what is the linear formula for loudness normalization
A
DSL
15
Q
what are the 4 nonlinear formulas for loudness normalization
A
- LGOB
- IHAFF
- FIG 6
- DSL
16
Q
what are the linear prescriptive strategies
A
- 1 target per frequency
- –same gain-frequency curves for all input levels
- —-until output level is high enough to limit (OLC)
- similar reserve gain recommendations across strategies
- similar in prescription of reduced low-frequency gain
- –to help reduce upward spread of masking from LF ambient noise
17
Q
lybarger’s half-gain rule
A
linear
*prescribed gain is 1/2 the amount of the HL
18
Q
Berger’s half-gain rule
A
linear
- 1/2 gain at most frequencies
- more than 1/2 gain at 1000 and 2000
19
Q
prescription of gain and output (POGO)
A
linear
- 1/2 gain with additional low cuts
- for losses up to 80dB HL
20
Q
POGO II
A
linear
- severe to profound losses
- gain increased by 1dB for every 1dB increase in HL
21
Q
libby one-third gain rule
A
linear
- gain prescribed is 1/3 of the HL
- less gain at low frequencies
22
Q
national acoustics laboratory- revised (NAL-R)
A
linear
*slightly less than 1/2 gain is prescribed
23
Q
NAL-RP
A
linear
- revised; profound
- less high frequency emphasis at 2 kHz as threshold increases beyond 90dB HL
24
Q
desired sensation level (DSL)
A
linear
- mild to severe losses; targets are 1 SD below the pt’s estimated MCL
- profound losses; based on experimentally optimal sensation levels
25
what is the nonlinear fitting strategy
* compression-based fitting methods
| - --provide more than 1 target/frequency
26
loudness growth at half-octave bands (LGOB
* nonlinear prescriptive strategy
* goal: loudness normalization
* HI pt categorizes loudness of NBN using a 7-pt likert scale
* for each input level, gain needed to normalize loudness is deduced
27
IHAFF
* nonlinear prescriptive strategy
* independent hearing aid fitting forum
* goal: loudness normalization
* use contour loudness scale
28
VIOLA
*nonlinear prescriptive strategy
| visual input-output locator algorithms
29
FIG 6
* nonlinear prescriptive strategy
* goal: loudness normalization
* requires only audiometric thresholds
* prescribes insertion and coupler gain for:
- --soft
- --conversational
- --loud input levels
30
DSL [i/o]
* desired sensation level [input/output]
* nonlinear prescriptive strategy
* goal: prescribe the appropriate amount of gain so that all acoustic signals fall within the pt's DR
* originally designed to meet the needs of the pediatric hearing aid population
31
the two alternative approaches of DSL
* DSL linear
- --loudness equalization
* DSL curvilinear
- --loudness normalization
32
DSL [i/o] (version 4)
nonlinear prescriptive strategy
| *curvilinear procedure became dominant method
33
DSL [i/o] (version 5)
* nonlinear prescriptive strategies
* CT increased based on the level of HL
* gain reduction with low-level noise (ie, expansion)
* consideration of loudness summation for OSPL90 prescription
* gain increase for conductive HL
* lower for adult
34
DSL prescriptive strategies in general
* used with kids most often
- --specify more information than with other strategies
- --more high and low frequency gain than other fitting methods
- --lower OPSL90 targets
35
NAL-NL1 and NAL-NL2
* nonlinear prescriptive strategies
* extension o NAL-R linear fitting strategy
* goal: maximize speech intelligibility
* used most often with adult patients
36
NAL-NL2
* nonlinear prescriptive strategies
* came out in 2010
* males are prescribed slightly more gain than females
* increases or decreases gain based on HA experience level
* gain for children is adjusted 5 dB higher at mid-level inputs compared to gain for adults; more than 5dB higher at low level inputs; less than 5dB higher at high level inputs
* bilateral fittings are prescribed less gain than unilateral fittings
* can select tonal or non-tonal languages
37
CAMEQ2
* nonlinear prescriptiVe strategy
* now called CAM2
* earlier versions
- --cambridge loudness equalization (CAMEQ)
- --cambridge restoration of loudness (CAMREST)
* loudness equalization approach
* attempts to limit the total loudness to be= that perceived by a normal hearing listener to the same sound
* predicts from the threshold the amount of gain needed
38
prescribing compression thresholds
* lower CT results in higher gain for low intensity sounds
| * around 60 dB SPL
39
prescribing OSPL90
* most effective method for prescribing OSPL90
* measure UCLs (LDLs) at specific frequencies
* use prescriptive formulas to determine appropriate OSPL90s
40
what is testing of electroacoustic performance
*measure of the output HA with inputs of various frequencies and intensities
41
what is the standards for electroacoustics
ANSI
42
what is the purpose of testing electroacoustic performance
to compare manufacturer specifications of HA to the electroacoustic characteristics of HA
43
forms of electroacoustic measurement
* EA measurements can be made in the coupler or in situ
* measure HA performance and compare performance to manufacturer spec sheet or prefit measurement
- --ANSI tests (coupler)
* verify HA output/settings are appropriate for the pt
- --simulated real-ear measurements (coupler)
- --real-ear measurements (in situ)
44
Electroacoustic testing of HA requires (4 things)
1) sound source that is calibrated
2) means to couple HA to measuring microphone
3) processing device to control measurement
4) method to display results
* *1-3 take place within a test box**
45
what are the possible sound sources for electroacoustic testing of HAs
* puretone
- --125-8kHz
- --40-90 dB SPL
* broadband
- --white noise
- --pink noise
* speech signals
- --recorded
- --live
- ---ICRA
* presented via external loudspeakers or loudspeakers located within test box
46
what is ICRA signal
* speech sound processed so that detail providing intelligibility to speech signal is removed
* however, temporal fluctuations in amplitude remain intact
47
means of coupling for electroacoustic testing of HA
* 2cc coupler
- --HA connective to one end
- --microphone connected to the other
* HA1 2cc coupler (CICs)
* HA1 2cc coupler with TRIC adapter (RIC)
* HA2 2cc coupler (BTEs?)
* real-ear probe-mic assembly
- --in-situ measurements
* occluded ear simulator (ANSI s3.25-R2003)
- --has same variation of impedance with frequency as the average ear
* Acoustic manikin (ANSI S3.35-2004)
- --knowles electric manikin for auditory research (KEMAR)
- ----ear simulators are located inside manikin
48
processing device for electroacoustic testing of HAs
* coupler microphone
- --measures sound coming from HA
* control microphone
- --aka reference mic
- --monitors the SPL reaching HA from loudspeaker
49
9 test box measurements that can be run
* calibration
* frequency response
* multicurve view
* input-output
* total harmonic distortion
* directionality
* internal noise
* magnetic response
* battery drain
50
frequency response with a standard ANSI curve
* HA at full-on gain
* no features activated
- --HA has not been programmed at this point
- --essentially how HA performs "off the shelf" without being programmed
- --can run this test initially on HA, but how can I run this test again if pt reports HA is not working
- ----if possible in manufacturer software, disable all features and put HA into FOG
- ----if not possible, run a gain curve using the ANSI test protocol
51
frequency response with gain-frequency response curve
* displays output of HA across frequencies for a specified input intensity
* similar to ANSI curve, but HA has now been programmed to pt
* typically measured with a 60 dB input intensity
- --full-on gain
- --reference-test setting
52
frequency response with OSPL90 frequency response curve
*ANSI S3.22 specifies HA maximum output should be measured using a 90 dB SPL input signal
53
input-output curves
shows the output level vs the input level for one frequency
54
harmonic distortion
when the input is a sine wave, distortion products occur at freqs that are harmonics of the input frequency
55
total harmonic distortion
the power of all distortion products summed and expressed relative to the power of the wanted output signal component
56
why measure distortion
* make sure HA meets manufacturer's specifications
* compare fidelity of two different HAs
* determine if HA uses peak clipping or output compression
* determine highest input level that can pass through HA without causing significant distortion
57
electroacoustic test measures of directionality
measures the amount of sound attenuated from the rear relative to sound from the front when directional mics are engaged
58
what does verifying directionality of mics depend on?
* algorithm used by manufacturer
* can you force aids into directional mode
- --auto function or auto-adaptive directional mics
- ----cannot verify that HA is actually switching to directional mode
- --manual program?
* front-back vs front-side
59
magnetic response electroacoustic test measurement (basic what is it)
measurement of SPL produced by HA with a t-coil
60
how are results of magnetic responses displayed
* graph of output SPL vs frequency for the specified magnetic input
* numerical value: represents the change in gain needed to produce output similar to that with the HA microphone
61
how is run magnetic response test box measure
* test box must contain a magnetic loop to generate a magnetic field
* can measure in a vertical or a horizontal field
62
measuring magnetic response in a vertical field
* SPLIV= SPL for a vertical inductive field
* ETLS= equivalent test loop sensitivity
- --calculated:
- ----the output signals for T-coil minus the output signal for an acoustic input level of 60dB
- ----basically describe how much the pt would have to change the volume control so that the acoustic output= t-coil output when listening via the mic
63
measuring magnetic response in a horizontal field
* SPLITS: SPL for an inductive telephone simulator
* RRSETS: relative simulated equivalent telephone sensitivity
- --calculated:
- ----the output signal for t-coil minus output signal for an acoustic input level of 60 dB
- ----basically describe how much the pt would have to change the volume control so that the acoustic output= t-coil output when listening via the mic
64
what should I do standard on every patient?
* before pt comes in: test box measures
- --ANSI
- --gain curve
- --d-mics
* on HAC/HAS;
- --gain curve (test box)
- --d-mics (test box)
- --validation
* after pt comes in: real ear measures
- --REAR (55, 65, 75, MPO)
- --d-mics (on ear)
- --validation
- --gain curve
65
explain validation vs verification
* validation is typically subjective measures
- --benefit/ success scales
* verification is objective measures
- --test box measures, probe microphone measures
66
two more terms for real-ear measures (REM)
* probe mic measures
| * speech mapping
67
potential ethics violation with real ear measures
* code of ethics refers to how we perform clinical audiology
* AAA Code:
- --principle 2=members shall maintain high standards of professional competence in rendering services
- --principle 4= members shall only provide services and products that are in the best interest of those served
* AAA's guidelines for audiologic management of adult hearing impairment
- --REM is currently the best method for establishing the output of a hearing aid in an individual ear in the hearing aid fitting process
- -it is unlikely that the pt knows this
- --if this procedure is not included in the HA fitting, yet the price of the hearing aids included the fitting, has the pt been charged appropriately because of a procedure documented as best practice was not performed
68
what is the purpose of probe mic measures?
* verification of HA performance
- --measures performance of HAs in situ (REMs)
- --estimate performance of HAs in 2-cc coupler (S-REMs)
* provide individualized correction factors for maneuvering among the various dB measures used in clinical audiology
69
potential issues with REMs
* potential problems with using REMs to verify HA output
* prescriptive targets are based on averages
- --not all pts will be satisfied with the outputs that match the prescriptive targets
* probe tube placement can cause variability in the measured output
70
rationale for REMs
* why not just aided thresholds to verify a user's performance with HAs?
- --speech does not occur at threshold
- --REMs provide an objective measure
- --aided thresholds are not (usually) ear specific
71
test environment for REM
* relatively quiet room (does not have to be sound insulated)
* do not seat pt next to any reflective surface
- --for example, a wall or mirror
72
instrumentation for REM
* probe-mic assembly
- --reference mic
- --probe mic
- -----with probe tube
* RECD transducer
* HA in situ
* alternatively, HA in 2-cc coupler
73
calibration of probe-mic assembly
* must calibrate 1st
| - --probe-mic and tubing do not have a flat frequency response
74
placement of probe tube
* set marker on probe tube
* reference mic should face out
* pass tube in front of blue cord and into EAC
* tip of probe tube: 2-5 mm from TM
75
positioning of the pt for REM
* sit no more than 3ft (1 meter) away from loudspeaker
* loudspeaker should be placed at 0-degrees azimuth
* pts tend to move throughout testing
- --may have to repostion pt throughout testing
76
probe mic measures without HA
* RECD
* REUR
* REUG
77
probe mic measures with HA in place
* REAR
* REAG
* READ 85 or REAR90
* REOR
* directionality
78
what is the calculated probe measure
*REIG
79
measurement signals for real ear measures
* pure tones
- --125-8kHz
- --40-90 dB SL
* broadband
- --pink noise
* speech signals
- --recorded
- --live
- --international collegium of rehabilitive audiology (ICRA)
80
REUR
* real ear unaided response
* SPL in the open (unaided) ear canal for a given stimulus
* clinically, REUR provides a reference for REAR
* taken into account when REIG is calculated
81
REUG
* real ear unaided gain
* difference in dB between real ear unaided response and stimulus signal SPL
* REUR minus test signal (dB SPL)
82
REIG
* real ear insertion gain
* not a measurement, but a calculation
* difference b/t aided and unaided ear canal SPL
* the amount of gain provided by the HA alone calculated by subtracting the REUG from the REAG across frequencies
- --or by subtracting the REUR from the REAR across frequencies
83
REIG calculations
* REIG=REAG-REUG
- --REAG=REAR-stimulus
- ----[REAR=SPL at TM without amplification]
- ----SPL at TM with amplification-stimulus
- --REUG=REUR-stimulus
- ----[REUR=SPL at TM without amplification]
- ----SPL at TM without amplification-stimulus
* REIG=[SPL at TM with amplification-stimulus] minus [SPL at TM without amplification-stimulus]
- ----=SLP at TM without amplification-SPL at TM without amplification
- ----=REAR-REUR
84
RECD
* real ear to coupler difference
* SPL generated in the pt's ear canal minus SPL generated in a 2cc coupler
* RECDs reveal the difference between the way the HA will perform in an individual's ear compared to the way it performs in a 2cc coupler
* derived by comparing real-ear SPL for a given test signal to the 2cc coupler SPL
* use insert phones and RECDs for the most accurate HA fitting
- --on all pts, not just pediatrics
85
what do RECDs allow you to do
* predict HA output in the ear canal when 2cc coupler values are known
* determine desired OSPL90 and coupler output settings
* stimulate real ear measurements from 2cc coupler measures
* individuals RED correction as to provide a better estimate of hearing thresholds for calculation of real ear prescriptive targets
86
troubleshooting reduced low frequency values with RECD
* let foam tip expand completely
* reseat the earmold
* use earmold lubricant
* check impedance results
87
troubleshooting reduced high frequency values for RECD
* probe tube may be too shallow
| * earmold RECDs usually roll off after 2k
88
troubleshooting large negative values across all frequencies for RECD
* probe tube may be plugged or dislodged from real ear module
* wrong probe mic selected
* check connections
89
REAR
* real ear aided response
| * SPL in the ear canal for a given stimulus, with a working HA in place
90
fitting tips and protocol for REAR
*conduct speech mapping with all special features activated (with the exception of frequency lowering, this should be deactivated)
1) enter pt's audio and measured LDL (if using DSL prescriptive approach)
2) select validated prescriptive formula (DSL or NAL) and variables (such as age and gender)
3) program HA to desired prescriptive formula
4) select appropriate speech or speech-like signal
5) calibrate probe tube if necessary, position pt, position probe tube at correct depth in ear canal
6) place device in ear canal (earmold, dome, or custom HA)
7) begin testing
8) adjust frequency-specific gain to achieve a reasonable target
9) continue until a match is obtained for all 3 input levels--do a final check to make sure that changes for input did not significantly affect the other two inputs
91
REAG
* real ear aided gain
* difference between REAR and the stimulus SPL
* REAG=REAR minus stimulus SPL
* same uses as REAR
92
REAR 85 or REAR90
* max SPL HA delivers to HA user's ear
* previously known as real ear saturation response
* used to ensure MPO does not exceed pt's LDL and to make sure MPO is not unreasonable low or restricting headroom
93
REOR or REOG
* real ear occluded response or gain
* for verifit 2:
- --EM or custom HA in pt's ear
- --turn HA off
- --pt vocalizes sustained "ee"
- --stop test
* for aurical freefit
- --use the occluded response test screen to measure the client's response with the hearing instrument in the ear but not turned on
- --compare REAG with the REOG you can find out what extent the HA blocks out sound from the ear canal
- --it can be assumed that sound passing the HA to get into the ear is proportional to the amount of sound that escapes past the hearing instrument from inside the ear
- --useful to know how much sound escapes from the ear in order to predict feedback problems
- --you can use this info to determine whether vents in the HA are appropriate size
94
pediatric patient with real ear measures
* verification
- --real ear measures are preferred
- --behavioral measures to corroborate REMs
- ----aided thresholds, speech tasks, behavioral observations
* REM requirements
* Pediatric HA targets: use DSL prescriptive formula
* limiting the output
- --safe limit: never exceed 124 dB SPL
- --DSL has lower OSPL90 targets
* alternative to real ear measurements
- --S-REMs
- -----levels measured in the 2cc coupler are converted to estimated ear canal levels using RECD values
- ----must measure RECD
95
adults patients
*real ear measures
---RECD= not a requirement for verifying real-ear measures but can make estimated HL in SPL more accurate
-----especially helpful if patients have unusual ear canal acoustics and can result in more accurate target estimation for use in the HA fitting
---REAR for soft, moderate and loud sounds
MPO measurement= some systems call this an 85 tone sweep
---typically use adult prescriptive formula= NAL-NL2
96
probe mic measures for open canal fits
* verification of open and closed fittings are similar
- --except the calibration process
- --uses a stored modified-pressure equalization approach
- --on most equipment simply select "open" or similar descriptor for HA style
- --some equipment will require you to conduct stored-equalization free-field calibration prior to conducting speech mapping
97
verification of MPO
* completed using REAR approach described earlier (REAR85 or 90 with swept pure tones)
* if output is either too high or too low, make appropriate changes and retest until REAR85 output falls to desired levels
98
verification of directionality
* program HA to "fixed directional" setting
* disable digital noise reduction if using noise as test signal
* have pt seated in usual test position (0 degrees azimuth)
* conduct REAR measure using desired test signal
* turn pt around 180 degrees and conduct a second REAER at the same input level from the back
* compare the two outputs
99
verification of digital noise reduction
test signal: noise (white, pink, or other noise available on equiptment)
1) conduct a REAR with DNR turned off using 75dB input to establish baseline
2) program HA to DNR planned for everyday use
3) conduct a 2nd REAR--leave noise on for at least 10 seconds
4) note the difference from baseline to maximu, reduction
100
verification of frequency lowering
* conduct REAR for 65dB input for reference
- --frequency lowering turned off
- --DNR turned off
* if your equipment has /s/ stimulus, present it at 65dB SPL
* if the stimulus does not fall above the pt's threshold, frequency lowering may need to be activated
* activate frequency lowering and note any change that occurs
* optional: play a slightly lower frequency stimulus and make sure pt can distinguish between the two sounds (example= /sh/)
