A smartphone app-based digital hearing aid with sliding-band dynamic range compression

Listeners with sensorineural hearing loss have degraded speech perception due to frequency-dependent elevation of hearing thresholds, reduced dynamic range, and increased temporal and spectral masking. Signal processing in hearing aids for such listeners uses frequency-selective amplification and dynamic range compression for restoring normal loudness of low-level sounds without making the high-level sounds uncomfortably loud. Sliding-band compression has been reported earlier for reducing the temporal and spectral distortions generally associated with currently used single and multiband compression techniques. The paper presents implementation of sliding-band compression as a smartphone app for use as a hearing aid. The processing involves a frequency-dependent gain function calculated on the basis of critical bandwidth based short-time power spectrum and the specified hearing thresholds, compression ratios, and attack and release times. It is realized using FFT-based analysis-synthesis and can be integrated with other such techniques for computational efficiency.