System and method for noise reduction having first and second adaptive filters responsive to a stored vector

• US 7,099,822 B2
• Filed: 08/12/2004
• Issued: 08/29/2006
• Est. Priority Date: 12/10/2002
• Status: Active Grant

• Current Assignee: F Poszat Hu LLC (Intellectual Ventures LLC)
• Original Assignee: Tranzeo Wireless Technologies Inc. (Charlotte Resources Ltd.)
• Inventors: Zangi, Kambiz C.
• Primary Examiner(s): Storm, Donald L.
• Application Number:
  US10/916,994
• Publication Number:
  US 20050251389A1
• Time in Patent Office: 747 Days
• Field of Search: None
• US Class Current: 704/226
• CPC Class Codes: G10L 2021/02082 the noise being echo, reverberation of the speech
• CPC Class Codes: G10L 2021/02166 Microphone arrays; Beamforming
• CPC Class Codes: G10L 21/0208 Noise filtering

Abstract

A system for microphone noise reduction includes first and second filter portions and a control processor adapted to adapt the first and second filter portions in response to a one of a plurality of stored vectors. Each stored vector is representative of acoustic transfer functions in accordance with a model of a vehicle and a respective position within the vehicle. A method for processing microphone signals includes selecting a vehicle model, selecting positions within the vehicle model, measuring acoustic response vectors at the positions, storing the response vectors, selecting one of the response vectors, and adapting first and second filter portions in accordance with the selected response vector.

Claims

1. A system, comprising:

a first filter portion configured to receive one or more input signals and to provide a single intermediate output signal;

a second filter portion configured to receive the single intermediate output signal and to provide a single output signal; and

a control circuit configured to receive at least a portion of each of the one or more input signals and at least a portion of the single intermediate output signal and to provide information to adapt filter characteristics of the first and second filter portions, wherein the control circuit is configured to automatically select one of a plurality of stored vectors having vector elements, wherein the selected one vector is used by the control circuit to generate the information to adapt the filter characteristics wherein each one of the vector elements is associated with a transfer function between a respective one of the one or more input signals and a reference input signal from among the one or more input signals.

2. The system of claim 1, wherein the control circuit comprises a first adaptation processor for providing first information to adapt the filter characteristics of the first filter portion and a second adaptation processor for providing second information to adapt the filter characteristics of the second filter portion.

3. The system of claim 2, wherein the first information corresponds to a noise power spectral density of the one or more input signals and the second information corresponds to one or more of:

a power spectral density of a noise portion of the intermediate output signal, a power spectral density of a desired signal portion of the intermediate output signal, or a power spectral density of the intermediate output signal.

4. A system, comprising:

a first filter portion configured to receive one or more input signals and to provide a single intermediate output signal;

a second filter portion configured to receive the single intermediate output signal and to provide a single output signal; and

a control circuit configured to receive at least a portion of each of the one or more input signals and at least a portion of the single intermediate output signal and to provide information to adapt filter characteristics of the first and second filter portions;

at least one discrete Fourier transform (DFT) processor coupled to the first filter portion and the control circuit to receive one or more time domain signals and to provide the one or more input signals in the frequency domain to the first filter portion, and to provide the at least a portion of each of the one or more input signals in the frequency domain to the control circuit; and

an interpolation processor coupled between at least one of the first filter portion and the control circuit and the second filter portion and the control circuit, to receive signal samples generated by the control circuit having a first frequency separation, to interpolate the signal samples generated by the control circuit, and to provide interpolation signal samples to at least one of the first filter portion and the second filter portion, having a frequency separation less than the frequency separation of the signal samples generated by the control circuit, wherein the control circuit comprises a first adaptation processor for providing first information to adapt the filter characteristics of the first filter portion and a second adaptation processor for providing second information to adapt the filter characteristics of the second filter portion, and wherein the first information corresponds to a noise power spectral density of the one or more input signals and the second information corresponds to one or more of a power spectral density of a noise portion of the intermediate output signal, a power spectral density of a desired signal portion of the intermediate output signal, or a power spectral density of the intermediate output signal.

5. A method for processing one or more microphone signals provided by one or more microphones associated with a vehicle, comprising:

selecting a vehicle model;

selecting one or more positions within a vehicle having the vehicle model;

measuring a respective one or more response vectors with an acoustic source positioned at selected ones of the one or more positions, wherein each of the one or more response vectors has respective vector elements, and wherein each one of the one or more response vectors is representative of a transfer function between a respective one of the one or more microphone signals and a reference microphone signal from among the one or more microphone signals;

storing the one or more response vectors;

selecting one of the stored response vectors; and

adapting a first filter portion and a second filter portion in accordance with the selected response vector.

6. The method of claim 5, wherein the measuring a respective one or more response vectors comprises:

collecting the one or more respective microphone signals at selected ones of the one or more positions;

estimating a plurality of cross power spectrums between each of the one or more microphone signals and a reference one of the one or more microphone signals for each of the one or more positions;

estimating a reference power spectrum of the reference one of the one or more microphone signals for each of the one or more positions; and

estimating a respective plurality of vector elements for each of the one or more response vectors, each vector element a ratio of a respective one of the plurality of cross power spectrums and the reference power spectrum.

7. The method of claim 5, wherein the selecting one of the stored response vectors comprises:

computing a respective error sequence associated with each element of each one of the stored one or more response vectors;

computing a respective error term associated with each one of the stored one or more response vectors in accordance with the computing a respective error sequence; and

selecting a response vector from among the stored one or more response vectors, wherein the selected response vector has a smallest respective error term.

8. The method of claim 7, wherein the selecting the response vector from among the stored one or more response vectors is performed at a time when at least one of the one or more microphone signals has a signal to noise ratio greater than a second predetermined value.

9. The method of claim 5, wherein the adapting the first filter portion and the second filter portion comprises:

adapting a response of the first filter portion in response to a noise portion of the one or more microphone signals and adapting a response of the second filter portion in response to a power spectral density of at least one of a noise portion of an output from the first filter portion, a desired signal portion of the output from the first filter portion, and characteristics of the output from the first filter portion.

10. The method of claim 5, wherein the measuring the respective one or more response vectors is performed at a time when at least one of the one or more microphone signals has a signal to noise ratio greater than a predetermined value.

11. The method of claim 5, wherein the selecting one of the stored response vectors is performed at a time when at least one of the one or more microphone signals has a signal to noise ratio greater than a predetermined value.