Single-channel noise reduction with pitch-adaptive post-filtering

Single-channel noise reduction for speech enhancement is often applied in cellular and in hands-free telephones. For speech distortions to be minimal, single-channel systems based on spectral subtraction cannot entirely eliminate environmental noise. A relatively high spectral noise floor has to remain in the speech signal. For further reduction of annoying noise components, pitch-adaptive post-filtering is investigated in this paper. The basic idea is to attenuate during voiced parts of speech the spectral valleys between the pitch frequency and the harmonics. Simulation results for a spectral-subtraction scheme in conjunction with a pitch-adaptive post-filter are given. A frequency-domain subband filtering scheme is shown to be capable of enhancing speech signals disturbed by car noise.