Implementation of a Digital Hearing Aid with User-Settable Frequency Response and Sliding-Band Dynamic Range Compression as a Smartphone App

Persons with sensorineural hearing loss suffer from degraded speech perception caused by frequency-dependent elevation of hearing thresholds, reduced dynamic range and abnormal loudness growth, and increased temporal and spectral masking. For improving speech perception by persons with moderate loss of this type, a digital hearing aid is implemented as an Android-based smartphone app. It uses sliding-band dynamic range compression for restoring normal loudness of low-level sounds without making the high-level sounds uncomfortably loud and for reducing the perceptible temporal and spectral distortions associated with currently used single and multiband compression techniques. The processing involves application of a frequency dependent gain function calculated on the basis of critical bandwidth based short-time power spectrum and is realized using FFT-based analysis-synthesis. The implementation has a touch-controlled graphical user interface enabling the app user to fine tune the frequency-dependent parameters in an interactive and real-time mode.