MULTI-BAND NOISE REDUCTION SYSTEM AND METHODOLOGY FOR DIGITAL AUDIO SIGNALS

摘要

The present invention relates to a multi-band noise reduction system for digital audio signals producing a noise reduced digital audio output signal from a digital audio signal. The digital audio signal comprises a target signal and a noise signal, i.e. a noisy digital audio signal. The multi-band noise reduction system operates on a plurality of sub-band signals derived from the digital audio signal and comprises a second or adaptive signal-to-noise ratio estimator which is configured for filtering a plurality of first signal-to-noise ratio estimates of the plurality of sub-band signals with respective time-varying low-pass filters to produce respective second signal-to-noise ratio estimates of the plurality of sub-band signals. A low-pass cut-off frequency of each of the time-varying low-pass filters is adaptable in accordance with a first signal-to-noise ratio estimate determined by a first signal-to-noise ratio estimator and/or the second signal-to-noise ratio estimate of the sub-band signal.

主权项

1. A multi-band noise reduction system for digital audio signals, comprising:
a signal input for receipt of a digital audio input signal comprising a target signal and a noise signal; an analysis filter bank configured for dividing the digital audio input signal into a plurality of sub-band signals Yk(n); a noise estimator configured for determining respective sub-band noise estimates {circumflex over (σ)}k2(n) of the plurality of sub-band signals Yk(n); a first signal-to-noise ratio estimator configured for determining respective first signal-to-noise ratio estimates ξk0(n) of the plurality of sub-band signals based on the respective sub-band noise estimation signals and the respective sub-band signals Yk(n); a second signal-to-noise ratio estimator configured for filtering the plurality of first signal-to-noise ratio estimates ξk0(n) of the plurality of sub-band signals Yk(n) with respective time-varying low-pass filters to produce respective second signal-to-noise ratio estimates ξk(n) of the plurality of sub-band signals Yk(n) wherein a low-pass cut-off frequency of each of the time-varying low-pass filters is adaptable in accordance with the first signal-to-noise ratio estimate and/or the second signal-to-noise ratio estimate of the sub-band signal; a gain calculator configured for applying respective time-varying gains Gk(n) to the plurality of sub-band signals Yk(n) based on the respective second signal-to-noise ratio estimates ξk(n) and respective sub-band gain laws to produce a plurality of noise compensated sub-band signals; and a synthesis filter bank configured to combine the plurality of noise compensated sub-band signals into a noise reduced digital audio output signal at a signal output.