Effect of Compression Ratio on Speech Recognition and Speech-Quality Ratings with Wide Dynamic Range Compression Amplification

This project examined the effect of varying compression ratio on speech recognition and quality. Both listeners with mild-to-moderate sensorineural hearing loss and a control group of listeners with normal hearing participated. Test materials were sentences from the Connected Speech Test (R. M. Cox, G. C. Alexander, & C. Gilmore, 1987) which were digitally processed with linear amplification and wide dynamic range compression amplification with 3 compression ratios. Speech-recognition scores were obtained with sentences in quiet and in noise at a 10-dB signal-to-noise ratio for each amplification condition. Additionally, the participants rated each amplification condition in terms of clarity, pleasantness, ease of understanding, and overall impression. Results indicated that, for speech in quiet, compression ratio had no effect on speech-recognition scores; however, speech-quality ratings decreased as compression ratio increased. For speech in noise, both speech-recognition scores and ratings decreased with increasing compression ratio for the listeners with hearing loss. These results suggest that selection of compression ratio on the basis of speech-quality judgments does not compromise speech recognition.