A combined approach for broadband noise reduction

This paper deals with broadband noise reduction for the restoration of audio recordings. The signals are processed in the frequency domain using the short-time Fourier transform. A method based on non-linear spectral subtraction is presented. To prevent the annoying phenomenon of musical noise which is caused by the noise suppression process, over-subtraction is applied to the degraded signal spectrum. This means that depending on the estimated signal-to-noise ratio (SNR) more than the average noise spectrum is subtracted. A masking threshold obtained by spectral smoothing of the degraded signal spectrum is used to determine the SNR. Furthermore, time-averaging is applied to the SNR. The averaging procedures in the time and frequency domain reduce the SNR variance. Therefore, audible processing distortions are reduced, too.