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Enhancement of word-recognition performance with a filtering technique
R H Wilson1, J P Preece, C S Crowther
1VA Medical Center, Long Beach, CA.
Journal of Speech and Hearing Research
|December 1, 1991
Summary
Notch filtering the NU No. 6 speech materials altered their level calibration, shifting psychometric functions in noise. This audio processing impacts speech perception testing for listeners with normal hearing.
Area of Science:
- Audiology
- Speech processing
- Psychoacoustics
Background:
- The NU No. 6 speech materials are commonly used in audiological testing.
- Understanding the impact of audio filtering on speech perception is crucial for accurate hearing assessments.
Purpose of the Study:
- To investigate the effect of notch filtering on the level calibration of NU No. 6 speech materials.
- To determine how this filtering influences psychometric functions in noise for normal-hearing listeners.
Main Methods:
- NU No. 6 speech materials were processed using a notch filter (247 Hz center, 34 dB depth).
- Amplitude changes were measured using a true vu meter.
- Psychometric functions were obtained for filtered and unfiltered materials in 60-dB SPL broadband noise from 12 normal-hearing listeners.
Main Results:
- Notch filtering reduced the amplitude range by 10 dB, equivalent to a 7.5-vu reduction.
- The filtering effectively changed the level calibration of the speech materials.
- Psychometric functions showed no change in slope but were displaced by an average of 5.8 dB towards lower sound-pressure levels for filtered materials.
Conclusions:
- Notch filtering significantly alters the perceived level of NU No. 6 speech materials.
- This level shift impacts speech detection/identification functions in noise, requiring adjustments in audiological testing protocols.
- Careful consideration of audio processing is necessary for reliable speech audiometry.