Effects of amplitude ramps on phonemic restoration of compressed speech with normal-hearing and hearing-impaired listeners

Continuity illusion refers to the phenomenon where an interrupted signal is perceived as continuous, once the silent interval is filled with a louder sound. A similar mechanism is believed to help with phonemic restoration of missing speech segments. When speech segments are not audible due to masking of interfering background sounds, listeners may fill in the gaps and have enhanced speech intelligibility, even when those segments are omitted. For example, as a special case of phonemic restoration, it was shown that recognition of gated sentences was better when the silent intervals were filled with loud noise bursts. The present study is a preliminary attempt in exploring hearing aid processing effects on complex listening tasks that are likely to occur in real life, such as restoration of obliterated speech. Specifically, we explored if phonemic restoration might be degraded due to hearing aid compression, which might produce ramps on the speech envelope during the recovery from compression following the loud noise bursts lling the gaps. In Experiment 1, phonemic restoration was measured with normal-hearing (NH) listeners where ramps of var- ying durations were added on the speech envelope after the noise intervals, to simulate recovery from compression. Phonemic restoration was significantly reduced as the duration of the ramps increased. Experiment 2 shows preliminary results with hearing-impaired (HI) listeners, where phonemic restoration was measured for a number of configurations. The results showed a large variability in phonemic restoration by HI listeners, and audibility and gating period were observed to be important factors affecting the results. The combined results imply that hearing aid compression might have detrimental effects on phonemic restoration; however, more data is needed to determine how applicable these results would be to HI listeners.