Speech with gaps: effects of periodic interruptions on speech intelligibility

This study examined the role of central auditory completion in speech understanding. The perception of periodically interrupted speech was investigated. For this purpose, gaps were inserted into speech signals by silencing out defined intervals. The main hypothesis was that word recognition increases with shorter gaps and is less influenced by the total amount of gaps.

Seventeen normal-hearing young adults took part in this study. Phrases from the German HSM speech recognition test were used as speech material. The examination comprised 220 modulated sentences presented binaurally at 65 dB. Intervals with durations ranging from 50 to 700 ms were taken to silence out 50, 65 and 80% of each sentence, respectively.

Mean speech perception values were in the range of 65-92%, 35-92% and 35-95% correct answers for gap ratios of 50, 65 and 80%, respectively. When comparing the same interval duration, word recognition was better for smaller gap ratios. Both, gap ratio and gap duration had a significant influence on identification performance.

Speech can be understood even when very large proportions are blanked out. A significant decrease in perception can be observed when gap duration exceeds more than half of the syllable length.