US 2004/0064307 A1 · Noise reduction method and device

Abstract

The invention concerns a method which consists, when analysing an input signal in the frequency domain, in determining a noise level estimator and a useful signal level estimator in an input signal frame, thereby enabling to calculate the transfer function of a first noise-reducing filter, carrying out a second pass to fine-tune the useful signal level estimator, by combining the signal spectrum and the first filter transfer function, then to calculate the transfer function of a second noise-reducing filter on the basis of the fine-tuned useful signal level estimator and the noise level estimator. Said second noise-reducing filter is then used to reduce the noise level in the frame.

Claims18

Dependent claims

A method for reducing noise in successive frames of an input signal (x(n)), comprising the following steps for at least some of the frames:

calculating a spectrum (X(k,f)) of the input signal by transformation to the frequency domain;
obtaining a frequency-dependent noise level estimator;
calculating a first frequency-dependent useful signal level estimator for the frame;
calculating the transfer function (Ĥ1(k,f)) of a first noise-reducing filter on the basis of the first useful signal level estimator and of the noise level estimator;
calculating a second frequency-dependent useful signal level estimator for the frame, by combining the spectrum of the input signal and the transfer function of the first noise-reducing filter;
calculating the transfer function (Ĥ(k,f)) of a second noise-reducing filter on the basis of the second useful signal level estimator and of the noise level estimator;
and
using the transfer function of the second noise-reducing filter in a frame filtering operation to produce a signal with reduced noise.

5 more elements

A device for reducing noise in an input signal (x(n)), comprising:

means (1-3) for calculating a spectrum (X(k,f)) of a frame of the input signal by transformation to the frequency domain;
means (5) for obtaining a frequency-dependent noise level estimator;
means (11) for calculating a first frequency-dependent useful signal level estimator for the frame;
means (13) for calculating the transfer function (Ĥ1(k,f)) of a first noise-reducing filter on the basis of the first useful signal level estimator and of the noise level estimator;
means (14-15) for calculating a second frequency-dependent useful signal level estimator for the frame, by combining the spectrum of the input signal and the transfer function of the first noise-reducing filter;
means (16) for calculating the transfer function (Ĥ(k,f)) of a second noise-reducing filter on the basis of the second useful signal level estimator and of the noise level estimator;
and
means (7-9) for filtering the frame by means of the transfer function of the second noise-reducing filter to produce a signal with reduced noise.

5 more elements

Dependencies are inferred from the claim text.

Noise reduction method and device

Life of this patent

Noise reduction method and device

Life of this patent

Abstract

Claims18