Optimizing speech enhancement by exploiting masking properties of the human ear

The problem of speech enhancement and mainly noise reduction in speech remains a key-point of hand-free telecommunications. A great number of techniques have been already put forward and for a few years an auditory model has been investigated in noise reduction. A new approach for enhancing a speech signal degraded by uncorrelated stationary additive noise is developed. In this approach the simultaneous masking effect of the human ear is exploited. Two states “noise masked/noise unmasked” are derived from a noise masking threshold computed using a rough estimate of the speech signal. Then a speech signal estimator is proposed as a weighted sum of the individual estimators in each state. The gain in the signal to noise ratio (SNR) and a distortion measure indicate some improvement in real noise conditions. Subjectively this improvement is noticeable only at high input SNRs