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29 Cards in this Set
- Front
- Back
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What is meant by "verifying a hearing aid"?
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Verification that prescribed hearing aid characteristics have been achieved in real ear of the patient.
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Applications of probe microphone measures
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Initial fitting: verification of frequency response and max output.
Verification of signal processing characteristics (e.g. directional microphone). Troubleshooting (e.g. occlusion effect). |
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List 4 methods of hearing aid verification
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Full verification (freq response/MPO): 1) Test box verification (avg real ear info), 2) Hybrid method (RECD + test box) - for kids, 3) Probe mic (real ear) measures - for adults.
4) Partial verification - functional gain - behavioral measures. |
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What information is used to verify hearing aid fitting entirely in the test box? What is the disadvantage of using this method?
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Average RECDs.
Not as accurate. Must account for difference between coupler and ear. There is too much variability between people's ears for this to be accurate. |
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How can real-ear measure be accurately simulated in the test box?
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RECD for the person. This is the difference between the coupler response and the persons ear canal response.
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How can RECD be used to fit a child with a hearing aid?
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Combine age-appropriate RECD with microphone effects to convert real-ear targets to 2cc coupler targets.
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What are microphone effects? How are these used in test box verification?
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When you measure the sound in the ear canal it changes based on where the microphone is located in relation to the ear.
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The lowest age at which adult RECD values can be used
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5 years
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Why are real ear measures necessary?
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So much variation between ears.
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How do you obtain REUG/R?
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Sound presented through a speaker, intensity level measure in open ear canal.
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How do you measure REAG/R?
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Intensity as a function of frequency measure in the ear canal (in sound-field) with the hearing aid in place and turned on.
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How do you measure REOG/R?
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Intensity as a function of frequency measure in the EAC with the HA in place and turned off.
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How do you measure REIG?
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The amount of gain delivered to the patient from the hearing aid that was not present without the aid. Difference between REAG and REUG
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Characteristics of the average REUG
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Two peaks.
Primary: 2700 Hz (17 dB) Secondary: 4000-5000 Hz (12-14 dB) |
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The primary purpose of REUG
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To serve as a reference for the calculation of real-ear insertion gain.
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How does REOG/R vary with style and venting of an earmold
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More open molds - less insertion loss.
More closed molds - more insertion loss. This is because REOR/G is with the HA in place and turned off, so it is just blocking the sound getting in. |
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Applications of REOG/R measurement
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Not a routine part of verification process. Used to determine attenuation properties of earplugs. Used to assess insertion loss from earmold.
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Probe tube positioning
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REIG - consistency of placement for REUG/REAG.
5mm past end of mold. Absolute depth- 28-30 mm past inter-tragal notch. REAR/G - accuracy in high frequencies affected by insertion depth. Distance past inter-tragal - 15-25/28 mm for measurement accuracy +/- 2 dB through 4000 Hz. |
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Requirement for test environment for real-ear measures
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Environment that minimizes reflective surfaces. Sound booth is best. Studies examining test environment. Reverberant room acceptable if loud speaker at a close distance (.5-1 m), low background noise, no reflective surfaces near measurement location.
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Probe tube insertion depth for infants/children
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<12 mon: 15 mm
1-5 yrs: 20 mm >5 yrs: 25-28 mm |
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What is functional gain?
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Based on behavioral thresholds. Difference between unaided and aided sound field thresholds. Analogous for insertion gain (for linear and CL aids). Should be considered supplement to, not replacement for REM.
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Disadvantages of functional gain measures
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Functional gain has variability. Behavioral thresholds. Head movement or change of body position can change the subject position in sound field --> different results.
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Advantages of probe-mic verification
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Test/re-test variability lower than FG measures (1-5 dB vs. 15 dB). Continuous frequency response, not just at specific frequencies. Can evaluate response at different input levels. Can verify real ear OSPL90. Faster than FG measures.
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Differences and similarities between functional gain and insertion gain
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Functional gain is a threshold measure, usually lower input signals used. Insertion gain is a suprathreshold measure, average input signals used. Agreement between FG and REIG will depend on HA use.
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Describe two circumstances when functional gain will not be equal to insertion gain
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FG overestimates REIG for WDRC (CT <60-65 dB). FG is a threshold measure (lower input signals than IG). WDRC has increased gain for low inputs and thresholds are measured as low inputs where as gain is lower at average inputs (where REIG is usually measured).
REIG overestimates FG when the patient has severe-profound loss with vibrotactile detection responses. Functional gain - based on perception. REIG - based on acoustics. Acoustic estimates inaccurate when there is no hearing. |
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SII
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Incorporates physical measure of speech across Hz. Weighting of speech for intelligibility. HF more important for intelligibility.
0.0 = no speech audible 1.0 = all speech audible 0.33 = approx. SII needed for SRT 0.6 = SII needed for about 80% recognition of words |
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Describe the difference between REUG and REUR. What is the feature that distinguishes these two terms?
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Gain is the difference between the SPL in the ear canal and the SPL at the reference mic.
Response is the SPL in the ear canal. For both the HA is in and turned on. |
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How do you measure RESR?
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Use a pure tone signal. This is because it is at the same level across frequencies. You cannot use speech because it is not at the same level at all frequencies.
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Which signals are recommended for REAR/REIG?
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Composite, quasi speech signal, speech.
65-70 dB average input. 50-55 dB soft input. You wouldn't use pure tones because the HA might think it is feedback and reduce the gain. |
