IHS Instrument Fitting 4 — Questions and Answers
Question 1: The input/output curve of a hearing aid with wide dynamic range compression (WDRC) shows gain decreasing as input level rises. This means the compression ratio:
- Is less than 1:1
- Is equal to 1:1 (linear)
- Is greater than 1:1 (Correct answer)
- Is infinite (limiting)
Correct answer: Is greater than 1:1
A compression ratio greater than 1:1 means output increases less than input, providing more gain for soft sounds and less for loud sounds.
Question 2: Which of the following best describes the attack time of a hearing aid compressor?
- Time for gain to decrease after a loud sound onset (Correct answer)
- Time for gain to recover after a loud sound ends
- Time for the microphone to activate
- Time delay before low-frequency processing begins
Correct answer: Time for gain to decrease after a loud sound onset
Attack time is how quickly the hearing aid reduces gain in response to a sudden loud input signal.
Question 3: A patient with a flat 50 dB HL hearing loss consistently rejects hearing aids because loud sounds are uncomfortable. The fitting adjustment MOST likely needed is:
- Increase attack time
- Lower the MPO/OSPL90 setting (Correct answer)
- Increase compression threshold
- Add a larger vent to the earmold
Correct answer: Lower the MPO/OSPL90 setting
Reducing the maximum power output (MPO) prevents the hearing aid from reaching uncomfortable loudness levels for the patient.
Question 4: In the context of hearing aid programming, 'acclimatization' refers to:
- Adjusting the hearing aid to outdoor temperature changes
- Gradually increasing gain over time to help new users adapt (Correct answer)
- Calibrating the device to a new audiogram
- Reducing feedback over the first few weeks of use
Correct answer: Gradually increasing gain over time to help new users adapt
Acclimatization features start with reduced gain and automatically or manually increase it as the user adjusts to amplification.
Question 5: When using a Knowles Electronic Manikin for Acoustic Research (KEMAR), the hearing aid fitting professional can:
- Test only ITE hearing aids
- Simulate real-ear measurements on a standardized head and ear canal (Correct answer)
- Measure tympanometry results
- Calibrate audiometers
Correct answer: Simulate real-ear measurements on a standardized head and ear canal
KEMAR is an acoustic manikin that allows real-ear simulation measurements in a controlled, repeatable environment.
Question 6: Which type of microphone configuration in a hearing aid provides the greatest directional benefit in a noisy restaurant?
- Omnidirectional microphone
- Single directional microphone
- Adaptive directional microphone (Correct answer)
- T-coil input
Correct answer: Adaptive directional microphone
Adaptive directional microphones continuously track and null noise sources from varying directions, providing superior SNR benefit in complex noise environments.
Question 7: When fitting a patient with a unilateral severe-to-profound hearing loss and normal hearing in the other ear, which device option routes sound from the impaired side to the better ear?
- BICROS fitting
- CROS fitting (Correct answer)
- Power BTE
- Bone-anchored hearing aid (BAHA) on the impaired side
Correct answer: CROS fitting
A CROS (Contralateral Routing of Signal) system transmits sound from the non-hearing side to the normal-hearing ear without amplification.
IHS Instrument Fitting 4
The input/output curve of a hearing aid with wide dynamic range compression (WDRC) shows gain decreasing as input level rises.
This means the compression ratio: