Increasing the intelligibility of speech through multiple phonemic restorations

Abstract

When gaps in speech are filled with noise, phonemic restorations (PhR's) may occur. Multiple PhR's follow rules governing “auditory induction” of nonverbal sounds, so that for maximal extent of illusory continuity of speech interrupted by noise, the noise must have the spectrum and amplitude corresponding to a potential masker of the speech. In addition, maximal illusory continuity occurs for speech with normal syntactic and semantic context [Bashford and Warren, Percept. Psychophys. 42, 114 (1987)]. The current study examines the effect of multiple PhR's upon speech intelligibility. When narrow-band CID (“everyday speech”) sentences were interrupted by periodic gaps, insertion of louder narrow-band noise into the gaps increased intelligibility, the greatest increase occurring when the noise band matched the speech in center frequency. A second experiment employed broadband speech with varying amounts of linguistic context (monosyllabic word lists, sentences with low predictability, and sentences with high predictability). Filling gaps with louder broadband noise improved the intelligibility of sentences, with the more predictable sentences showing the greatest restoration. However, noise did not restore intelligibility of word lists even when illusory continuity occurred. [Work supported by NIH and AFSOR.]