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Noise reduction with FM systems in FM/EM mode
1Mayo Clinic, Rochester, Minnesota.
Ear and Hearing
|February 1, 1994
Summary
New hearing aid technology using a prototype frequency-modulated (FM) auditory trainer significantly improved speech recognition in noise. This advanced system outperformed conventional devices by better separating speech from background noise.
Area of Science:
- Audiology
- Speech and Hearing Sciences
- Biomedical Engineering
Background:
- Conventional noise reduction hearing aids often fail to improve speech recognition in noisy environments.
- This limitation stems from single-microphone systems applying noise reduction equally to speech and noise, negating signal-to-noise ratio benefits.
- Existing hearing aid technology struggles to effectively enhance speech clarity amidst background noise.
Purpose of the Study:
- To evaluate a prototype frequency-modulated (FM) auditory trainer with adjustable microphone settings.
- To assess the effectiveness of a remote FM microphone combined with an ear-level environmental microphone (EM) for speech recognition in noise.
- To compare different configurations of the EM, including a high-pass filter, against standard settings.
Main Methods:
- Five subjects with moderate to severe sensorineural hearing loss participated.
- Speech recognition thresholds (SRTs) were measured under five conditions: FM only, EM with high-pass filter (EM-HP), EM with standard response (EM-S), combined FM/EM-HP, and combined FM/EM-S.
- The EM's frequency response was configured to either match the FM response or provide a high-pass filter characteristic.
Main Results:
- The FM-only condition yielded SRTs 9-10 dB better than either EM-only condition.
- Combined use of FM and EM with a high-pass filter (FM/EM-HP) showed an average improvement of 4 dB over the FM/EM-S condition.
- The prototype demonstrated superior performance in enhancing speech recognition in noise compared to EM-only configurations.
Conclusions:
- The prototype FM auditory trainer shows significant promise for improving speech recognition in challenging listening environments.
- Combining a remote FM microphone with an ear-level environmental microphone, particularly with a high-pass filter, offers enhanced benefits.
- This technology represents a potential advancement over current noise reduction hearing aids for individuals with sensorineural hearing loss.