Evaluation of the Phase-Inversion Signal Separation Method When Using Nonlinear Hearing Aids

Using two measurements with simultaneous speech and noise presentation, Hagerman and Olofsson have suggested a time-domain method to estimate the speech and noise signals at the output of a hearing device. The method, which uses a simple phase-inversion scheme, has gained popularity in hearing-aid research, although receiving only limited validation. In this work, we present an evaluation of this signal-separation method using simulated measurements with different hearing aids and listening conditions. Estimates of the speech and noise spectra from the phase-inversion method are compared to those obtained using the coherence function. New measures of speech and noise distortion are proposed as tools to evaluate the phase-inversion method. Additionally, we analyze the intelligibility predictions computed from the recovered spectral estimates, while accounting for the proposed speech distortion measure. Under additive-noise conditions, the phase-inversion method provides ideal signal separation without suffering any biases at low signal-to-noise ratios. For conditions involving automatic gain control, compressive output limiting, and peak clipping, the intelligibility predictions based on the phase-inversion method are found to agree with relevant findings from the literature.