Spatial influences on the spectral restoration of narrowband speech.

Abstract

In phonemic restoration, both perceived continuity and intelligibility of temporally interrupted speech improve with the addition of noise in the speech gaps. Perceived continuity decreases slightly when interrupted speech and “filler” noise are presented from different directions; however, a recent study found that intelligibility is not strongly influenced by spatial cues. A few studies have demonstrated spectral restoration: improvements in the intelligibility of speech that has spectral notches when band-passed filler noise is added to the spectral gaps. Here, we explored whether the spatial location speech and filler noise influence intelligibility in spectral restoration conditions. We tested intelligibility of two 3/4-wide speech bands in a variety of configurations. Control conditions included diotic presentation of a low-frequency speech band alone, a high-frequency band alone, and the two bands together. Intelligibility was poor for either band alone, but significantly better with the two bands together. When we added diotic noise to the spectral gap between the low- and high-frequency bands, intelligibility improved. Finally, when we presented the noise with an ITD so that it was perceived from off center, intelligibility was lower than when both filler noise and speech bands were diotic. Results demonstrate a spatial influence on spectral restoration.