A combined approach for broadband noise reduction

Abstract

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.