IHS Aid Technology 5 — Questions and Answers
Question 1: What is the purpose of an earmold acoustic horn (Libby horn) modification?
- To reduce low-frequency amplification
- To boost high-frequency gain by gradually expanding the bore diameter toward the canal tip (Correct answer)
- To increase the occlusion effect for better bass perception
- To prevent moisture from entering the hearing aid tubing
Correct answer: To boost high-frequency gain by gradually expanding the bore diameter toward the canal tip
A Libby horn is a stepped or flared bore in the earmold tubing that creates an acoustic resonance boosting high-frequency output, useful for high-frequency hearing loss.
Question 2: In the context of hearing aid programming, what does 'NAL-NL2' refer to?
- A noise-cancellation algorithm developed in Norway
- A prescriptive fitting formula developed by the National Acoustic Laboratories of Australia (Correct answer)
- A Bluetooth protocol for connecting hearing aids to loop systems
- A standardized earmold impression material specification
Correct answer: A prescriptive fitting formula developed by the National Acoustic Laboratories of Australia
NAL-NL2 (National Acoustic Laboratories Non-Linear version 2) is a widely used prescriptive fitting target that aims to maximize speech intelligibility while maintaining overall loudness comfort.
Question 3: Which of the following describes the function of a digital noise reduction (DNR) algorithm in hearing aids?
- It eliminates all background sound signals below 1000 Hz
- It reduces gain in channels identified as containing primarily non-speech noise (Correct answer)
- It filters out sounds louder than 85 dB SPL to prevent damage
- It removes electrical interference from nearby electronic devices
Correct answer: It reduces gain in channels identified as containing primarily non-speech noise
DNR algorithms detect channels with unfavorable speech-to-noise ratios and reduce gain in those channels to improve listening comfort, though they do not improve speech recognition scores.
Question 4: What does the OSPL90 measurement on a hearing aid specification sheet indicate?
- The output sound pressure level produced by the aid when the input is 90 dB SPL with the gain control at maximum (Correct answer)
- The maximum gain of the aid at 90 dB input with controls at reference test gain
- The frequency response of the aid measured in a 90 dB reverberant field
- The output level at which 90% of users report loudness discomfort
Correct answer: The output sound pressure level produced by the aid when the input is 90 dB SPL with the gain control at maximum
OSPL90 (Output Sound Pressure Level with a 90 dB input) represents the maximum output the hearing aid can produce and is used to ensure the aid won't exceed the patient's loudness discomfort level.
Question 5: A patient using a body-worn FM receiver with their hearing aids via direct audio input (DAI) asks why they still hear background noise. The most likely explanation is:
- DAI deactivates the hearing aid microphones automatically during FM use
- The hearing aid microphones remain active in most configurations, mixing local sound with the FM signal (Correct answer)
- The FM transmitter is not compatible with the hearing aid brand
- The hearing aid's telecoil is overriding the FM input
Correct answer: The hearing aid microphones remain active in most configurations, mixing local sound with the FM signal
Unless programmed to microphone-off mode, hearing aid microphones typically remain active during DAI/FM use, allowing the patient to hear both the remote FM signal and surrounding environmental sounds.
Question 6: Which technology allows hearing aids from the same manufacturer to share data and coordinate processing between the two ears in real time?
- Remote programming via cloud server
- Ear-to-ear (binaural) wireless synchronization (Correct answer)
- Dual-channel analog coupling
- Manual volume control mirroring
Correct answer: Ear-to-ear (binaural) wireless synchronization
Ear-to-ear wireless synchronization allows bilateral hearing aids to share microphone data and coordinate functions like directional processing, program changes, and volume adjustments in real time.
Question 7: What is the primary difference between a 'linear' and 'nonlinear' hearing aid amplifier?
- Linear aids use digital processing; nonlinear aids use analog processing
- Linear aids apply the same gain regardless of input level; nonlinear aids vary gain based on input level (Correct answer)
- Linear aids amplify all frequencies equally; nonlinear aids boost only speech frequencies
- Linear aids require custom earmolds; nonlinear aids use open domes
Correct answer: Linear aids apply the same gain regardless of input level; nonlinear aids vary gain based on input level
A linear amplifier provides a fixed amount of gain regardless of how loud or soft the input signal is, while a nonlinear (compression) amplifier varies gain to accommodate a wider range of input levels.
IHS Aid Technology 5
What is the purpose of an earmold acoustic horn (Libby horn) modification?