Sweet-Spot Compression: An Amplification Strategy for Improving Listening Outcomes at Moderate to High Levels

When speech increases in level from moderate to high, speech intelligibility (SI) can decrease. Termed rollover, this phenomenon is neglected during hearing aid (HA) fitting. A previous study introduced "sweet-spot compression" (SSC)-an amplification strategy for preventing rollover and improving listening outcomes at moderate to high levels. SSC aims to place speech in that area of an individual's performance-intensity function where both SI and listening comfort are high-the "sweet spot." To achieve this, it combines high compression ratios with long time constants to provide quasi-linear amplification in the sweet-spot area. Using a HA simulator, headphone presentation, and 16 participants with rollover, SSC previously outperformed a clinical reference condition in terms of listening outcome. Here, we extended this work by (a) mapping out individual differences in the most comfortable speech level (MCL) and SI in noise at moderate to high levels, and (b) evaluating the listening outcome with SSC further. Using a wearable research HA, we tested 18 randomly chosen participants with mild to moderate hearing loss. Our analyses showed clear individual differences in MCL and SI with linear amplification. SSC gave better SI and was clearly preferred in quiet and in noise relative to a clinical reference condition. At the group level, rollover did not occur for either SSC or the reference condition. At the individual level, we found fewer cases of rollover with SSC than with the reference condition. Overall, we conclude that SSC shows promise with respect to improving listening outcomes at moderate to high levels.