Patent ID: 6996524

Claim:
Speech enhancement device for the reduction of background noise, comprising a time-to-frequency transformation unit to transform frames of time-domain samples of audio signals to the frequency domain, background noise reduction means to perform noise reduction in the frequency domain, and a frequency-to-time transformation unit to transform the noise reduced audio signals from the frequency domain to the time-domain, characterized in that the background noise reduction means comprise a background level update block to calculate, for each frequency component in a current frame of the audio signals, a predicted background magnitude B[k] in response to the measured input magnitude S[k] from the time-to-frequency transformation unit and in response to the previously calculated background magnitude B −1 [k], a signal-to-noise ratio block to calculate, for each of said frequency components, the signal-to-noise ratio SNR[k] in response to the predicted background magnitude B[k] and in response to said measured input magnitude S[k] and a filter update block to calculate, for each of said frequency components, the filter magnitude F[k] for said measured input magnitude S[k] in response to the signal-to-noise ratio SNR[k]; wherein the previously predicted background magnitude is updated according to the relation: B[k]=max{min{B′[k], B″[k]}, B min }, with B min the minimum allowed background level, while B′[k]=B −1 [k]. U[k] and B″[k]=(B′[k].D[k])+(|S[k]|.C.(1−D[k])), in which U[k] and D[k] are frequency dependent scaling factors and C a constant.