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Noise reduction hearing aids: release from masking and release from distortion
1Department of Communication Disorders, University of Minnesota, Minneapolis.
Ear and Hearing
|April 1, 1992
Summary
Automatic frequency response (AFR) hearing aids may improve speech recognition in noise. This study found modest effects but highlighted potential benefits from reduced distortion and upward spread of masking.
Area of Science:
- Audiology
- Speech Science
- Hearing Aid Technology
Background:
- Hearing aids with Automatic Frequency Response (AFR) typically decrease low-frequency gain during noise.
- Previous research suggests AFR hearing aids enhance high-frequency speech recognition in low-frequency noise compared to non-AFR aids.
Purpose of the Study:
- To investigate the effects of AFR hearing aids on masking patterns and speech recognition in noise.
- To analyze hearing aid-generated distortion products in the ear canal.
Main Methods:
- Obtained masking patterns using frequency-modulated probe tones in low-frequency noise.
- Measured speech recognition thresholds for high-frequency monosyllables in the same noise.
- Utilized a master hearing aid with an AFR circuit and a laboratory simulation for testing.
Main Results:
- Modest AFR effects were observed in subjects wearing the master hearing aid.
- Significant hearing aid-generated distortion products were detected in the non-AFR condition.
- A low-distortion AFR simulation showed greater release from masking.
Conclusions:
- Improvements in speech recognition with AFR hearing aids may stem from reduced upward spread of masking.
- Reduction of hearing aid distortion products in the non-AFR setting also likely contributes to improved audibility.