Scene-Aware Dynamic-Range Compression in Hearing Aids

Wide dynamic-range compression (WDRC) is one of the essential building blocks in hearing aids and aims at improving audibility while maintaining acceptable loudness at high sound pressure levels for hearing-impaired (HI) listeners. While fast-acting compression with a short release time allows amplifying low-intensity speech sounds on short time scales corresponding to syllables or phonemes, such processing also typically amplifies noise components in speech gaps. The latter reduces the output signal-to-noise ratio (SNR) and disrupts the acoustic properties of the background noise. Moreover, the use of fast-acting compression distorts auditory cues involved in the spatial perception of sounds in rooms by amplifying low-level reverberant energy portions of the sound relative to the direct sound. Some of these shortcomings can be avoided by choosing a longer release time, but such a slowacting compression system fails to amplify soft speech components on short time scales and compromises on the ability to restore loudness perception. This chapter investigates the benefit of a new scene-aware dynamic-range compression strategy, which attempts to combine the advantages of both fast- and slow-acting compression. Specifically, the release time of the compressor is adaptively hanged to provide fastand slow-acting compression depending on whether the target was present or absent. The benefit of this scene-aware compression strategy was evaluated instrumentally in acoustic scenarios where speech and noise were present simultaneously. Moreover, a subjective listening test was conducted to assess the impact of scene-aware compression on reverberant speech signals by measuring the perceived location and spatial distribution of virtualized speech in normal-hearing (NH) listeners.