Influence of clinical fitting rationales on rollover at above-conversational speech levels

Hearing aids provide level-dependent gain to improve speech audibility. While more audibility typically leads to better speech intelligibility at low levels, several studies have found that at high levels increasing the presentation level can lead to decreased intelligibility. Termed rollover, this phenomenon has been observed in listeners with normal and elevated audiometric thresholds. In two previous studies, we presented linearly and non-linearly amplified speech in quiet at above-conversational levels to hearing-impaired listeners via headphones and observed rollover in many cases. In the current study, we investigated rollover under more ecologically valid conditions. A group of adults with sensorineural hearing losses were tested with a wearable hearing-aid simulator that was fitted according to the NAL-RP and NAL-NL2 gain prescription rules. Speech intelligibility in background noise was assessed using a free-field setup. We hypothesized that, at the group level, NAL-NL2 gains would lead to significantly less rollover than NAL-RP gains. To further our understanding of the mechanisms behind aided speech recognition at above-conversational levels, we compared our results to predictions based on the Speech Intelligibility Index. Here, we present initial data from an ongoing study.