Effects of spectral alternation on the intelligibility of words and sentences.

Abstract

In this study of a novel speech interference paradigm, it was found that periodic alternation between nonoverlapping filtering conditions (1100 Hz low-pass and 1700 Hz high-pass) significantly reduced intelligibility. Thus, although repetition accuracy for key words within sentences was approximately 98% with continuous low-pass or high-pass filtering alone, listeners averaged only 48% correct when frequency ranges alternated at a rate of 2.67 Hz. Interestingly, intelligibility improved by about 39% when low-pass noise was mixed with segments of high-pass speech and high-pass noise was mixed with segments of low-pass speech. A smaller increase due to added noise was also observed with spectrally alternated word lists. The interference produced by spectral alternation appears to be related to other verbal and musical phenomena, including stream segregation. The results from various control conditions indicate that the enhanced intelligibility produced by added noise involved phonemic restorations that occurred within each speech band, as well as a spectral completion effect that acted across spectral bands.