Noise Eliminating Apparatus

• US 20090214054A1
• Filed: 03/07/2006
• Published: 08/27/2009
• Est. Priority Date: 03/07/2005
• Status: Active Grant

• Current Assignee: TOA Corporation
• Original Assignee: TOA Corporation
• Inventors: Miyata, Satoshi, Fujii, Kensaku
• Granted Patent: US 8,180,068 B2
• Time in Patent Office: Days
• US Class Current: 381/94.100
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

A noise eliminating apparatus includes a first microphone, a second microphone and a signal processing unit, the signal processing unit includes a linear prediction filter and a noise resynthesis filter, the linear prediction filter receives an output signal of the first microphone, predicts the output signal of the first microphone by linear prediction and generates a prediction signal, and the noise resynthesis filter is an adaptive filter which receives, as a main input signal, a first difference signal obtained by subtracting one of the output signal of the first microphone and the prediction signal from the other, receives, as an error signal, a second difference signal obtained by subtracting one of an output signal of the second microphone and an output signal of the noise resynthesis filter itself from the other, and updates a filter coefficient so that the error signal is minimized.

Claims

1. A noise eliminating apparatus comprising a first microphone, a second microphone and a signal processing unit, wherein:

the signal processing unit includes a linear prediction filter and a noise resynthesis filter;

the linear prediction filter receives an output signal of the first microphone, predicts the output signal of the first microphone by linear prediction and generates a prediction signal; and

the noise resynthesis filter is an adaptive filter which receives, as a main input signal, a first difference signal obtained by subtracting one of the output signal of the first microphone and the prediction signal from the other, receives, as an error signal, a second difference signal obtained by subtracting one of an output signal of the second microphone and an output signal of the noise resynthesis filter itself from the other, and updates a filter coefficient so that the error signal is minimized.

2. The noise eliminating apparatus according to claim 1, wherein:

a coefficient vector of the noise resynthesis filter at a time j+1 is produced by adding an update vector to a coefficient vector at a time j; and

when a magnitude of the update vector determined by an adaptive algorithm applied by the noise resynthesis filter is larger than a predetermined value, the magnitude of the update vector is reduced so as to become the predetermined value without changing a direction of the update vector, and the coefficient vector of the noise resynthesis filter is updated by the reduced update vector.

3. The noise eliminating apparatus according to claim 1, wherein the adaptive algorithm applied by the noise resynthesis filter is a learning identification method.

4. The noise eliminating apparatus according to claim 1, wherein the linear prediction filter is an adaptive filter which receives the first difference signal as the error signal, and updates the filter coefficient so that the error signal is minimized.