Intelligibility of English Mosaic Speech: Comparison between Native and Non-Native Speakers of English

Abstract

Mosaic speech is degraded speech that is segmented into time × frequency blocks. Earlier research with Japanese mosaic speech has shown that its intelligibility is almost perfect for mosaic block durations (MBD) up to 40 ms. The purpose of the present study was to investigate the intelligibility of English mosaic speech, and whether its intelligibility would vary if it was compressed in time, preserved, or stretched in time. Furthermore, we investigated whether intelligibility differed between native and non-native speakers of English. English (n = 19), Indonesian (n = 19), and Chinese (n = 20) listeners participated in an experiment, in which the mosaic speech stimuli were presented, and they had to type what they had heard. The results showed that compressing or stretching the English mosaic speech resulted in similar trends in intelligibility among the three language groups, with some exceptions. Generally, the intelligibility for MBDs of 20 and 40 ms after preserving/stretching was higher, and decreased beyond MBDs of 80 ms after stretching. Compression also lowered intelligibility. This suggests that humans can extract new information from individual speech segments of about 40 ms, but that there is a limit to the amount of linguistic information that can be conveyed within a block of about 40 ms or below.