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The Effect of Nonlinear Frequency Compression on Acoustic Change Complex Responses in High-Frequency Dead-Regioned
1Department of Audiology, Near East University, Nicosia, Cyprus.
Journal of the American Academy of Audiology
|May 24, 2021
Summary
This study shows that hearing aid settings for frequency compression significantly impact cortical responses. Optimal adjustment, not default settings, is crucial for discriminating high-frequency sounds in hearing-impaired individuals.
Area of Science:
- Auditory Neuroscience
- Audiology
- Signal Processing
Background:
- High-frequency sounds are critical for speech understanding.
- Frequency compression in hearing aids aims to make high-frequency sounds audible.
- Cortical auditory evoked potentials, like the Acoustic Change Complex (ACC), offer insights into auditory processing.
Purpose of the Study:
- To investigate the cortical-level discrimination of high-frequency stimuli using frequency compression.
- To compare Acoustic Change Complex (ACC) responses in normal-hearing and hearing-impaired individuals.
- To evaluate the impact of different hearing aid frequency compression settings on ACC.
Main Methods:
- A case-control study design was employed.
- Acoustic Change Complex (ACC) recordings were made using 1000ms stimuli with 500 and 4000 Hz tones.
- Hearing aid parameters, including start frequency (SF) and compression ratio (CR), were manipulated (default, optimal, extra compression), and wave latencies were analyzed using independent samples t-tests.
Main Results:
- Acoustic Change Complex (ACC) was observed in all participants.
- Hearing-impaired individuals exhibited significantly longer ACC wave latencies compared to normal-hearing individuals.
- Statistically significant differences were found between various start frequency (SF) settings, but not between compression ratio (CR) settings.
Conclusions:
- Default hearing aid settings for start frequency (SF) and compression ratio (CR) are insufficient for discriminating high-frequency information at the cortical level.
- Optimal hearing aid fitting requires careful adjustment of bandwidth to avoid under- or over-compression.
- Acoustic Change Complex (ACC) can serve as a valuable tool alongside real-ear measurements for hearing aid fitting.
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