ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2pPP23. Effects of amplitude envelope expansion and compression on nonsense sentence recognition.

Richard L. Freyman

Debra Speicher

G. Patrick Nerbonne

Dept. of Commun. Disorders, Univ. of Massachusetts, 6 Arnold House, Amherst, MA 01003

When spectral information in speech is obscured, listeners presumably fall back on secondary cues such as those contained within the gross waveform envelope. This study examined the extent to which listeners' ability to use such cues is resistant to distortions of the envelope. Signal correlated noise samples, created individually to follow the amplitude envelopes of 200 nonsense sentences, were used as maskers of those sentences, with signal-to-noise ratios of -4, -2, 0, and +2 dB. The resulting waveforms preserved the original wideband envelopes, but spectral information was degraded to a degree determined by the S-N ratio. The sentences were presented monaurally to normal hearing subjects at 70 dB SPL. Recognition of key words in these sentences was compared to that obtained for waveforms that had been processed with two different levels of amplitude expansion and two levels of compression. The results indicated that amplitude expansion severely reduced recognition scores, while compression had little effect. [Work supported by NIH #DC01533.]