Telephone having improved hands free operation audio quality and method of operation thereof

US 20030099345A1
Filed: 11/27/2001
Published: 05/29/2003
Est. Priority Date: 11/27/2001
Status: Active Grant

First Claim

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1. A telephone having a hands-free mode of operation, said telephone comprising:

a first microphone receiving sound in hands-free mode, and providing first audio signals representative of received sounds to a first delay path;

a second microphone receiving said sounds in hands-free mode and providing second audio signals representative of said received sounds to a second delay path, said second microphone spaced a selected distance from said first microphone;

an adder combining said first audio signals from said first delay path with said second audio signals from said second delay path;

an analysis and control unit analyzing received said signals and adjusting delay through said second delay path; and

an adjustable filter receiving combined said signals from said adder and filtering noise from said combined signals.

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Abstract

A telephone having a hands-free mode of operation. The telephone includes a pair of microphones spaced apart from each other. Each microphone receives sound in hands-free mode of operation and provides audio signals representative of received sounds. The audio signals from each microphone may be converted to digital audio signals. The digital audio signals are presented to a fixed delay path and a variable delay path. Audio signals from both paths are combined and filtered in an adjustable filter to remove noise based upon a prior determination of the noise source location and the voice spectrum derived from the digital audio signals.

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17 Claims

1. A telephone having a hands-free mode of operation, said telephone comprising:
- a first microphone receiving sound in hands-free mode, and providing first audio signals representative of received sounds to a first delay path;
  
  a second microphone receiving said sounds in hands-free mode and providing second audio signals representative of said received sounds to a second delay path, said second microphone spaced a selected distance from said first microphone;
  
  an adder combining said first audio signals from said first delay path with said second audio signals from said second delay path;
  
  an analysis and control unit analyzing received said signals and adjusting delay through said second delay path; and
  
  an adjustable filter receiving combined said signals from said adder and filtering noise from said combined signals.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- - 2. A telephone as in claim 1 wherein said first delay path is a fixed delay path, said second delay path is a variable delay path and said first audio signals from said fixed delay path and said second audio signals from said variable delay path are digital audio signals.
  - 3. A telephone as in claim 2 wherein said fixed delay path provides a delay proportional to the selected distance between said first microphone and said second microphone.
  - 4. The telephone as in claim 2 wherein the variable delay inserts a delay having a range less than twice the delay of said fixed delay path.
  - 5. A telephone as in claim 1 wherein said adjustable filter is an adjustable digital filter providing a digital audio output.
  - 6. A telephone as in claim 2 wherein each of said fixed delay path and said variable delay path comprises:
    - an amplifier receiving an analog signal from a connected microphone; and
      
      an analog-to-digital converter (ADC) converting an output of said amplifier to a corresponding digital signal.
  - 7. A telephone as in claim 6 wherein said digital signal from said ADC in said variable delay path is provided to said analysis and control unit.
  - 8. A telephone as in claim 2 wherein said output from said fixed delay path is provided to said analysis and control unit.
  - 9. A telephone as in claim 2 wherein said analysis and control unit further sets filter values in said adjustable digital filter.
  - 10. A telephone as in claim 2 wherein the analysis and control unit comprises:
    - means for varying the delay of said adjustable delay path;
      
      determining means for determining a ratio of a voice signal to a background noise signal; and
      
      means for identifying an increase in said ratio responsive to delay changes in said adjustable delay path.
  - 11. A telephone as in claim 10 wherein said analysis and control unit further comprises:
    - means for extracting a noise spectrum from a first signal; and
      
      means for extracting a voice spectrum from a composite signal, extracted said voice spectrum being compared against said noise spectrum in said determining means.
  - 12. A telephone as in claim 11 wherein said adjustable digital filter is an adjustable bandpass filter and said analysis and control unit adjusts said adjustable bandpass filter to remove signals having frequencies outside of said extracted voice spectrum.

13. A method of controlling a speakerphone, said speakerphone having at least two microphones spaced a selected distance from each other, sound signals from each of said microphones being combined in said speaker phone and presented as a voice output from said speakerphone to a party at another end of a hands-free call, said method comprising the steps of:
- a) taking a noise baseline at each of said microphones, said noise baseline providing a noise frequency spectrum of background noise;
  
  b) taking a voice baseline at each of said microphones, said voice baseline providing a voice frequency spectrum of a speaker'"'"'s voice;
  
  c) comparing said voice baseline with said noise baseline to determine a substantially optimum delay for a signal path from one of said microphones;
  
  d) setting a delay in said signal path responsive to said optimum delay; and
  
  e) filtering noise associated with said noise spectrum.
- View Dependent Claims (14, 15, 16, 17)
- - 14. A method as in claim 13 wherein steps c) through e) are periodically repeated throughout a hands-free call.
  - 15. A method as in claim 14 wherein at least one idle time is identified in said hands-free call and, at each said at least one idle time a new noise baseline is extracted from signals from said microphones.
  - 16. A method as in claim 13 wherein the step c) of comparing said voice baseline with said noise baseline comprises the steps of:
    - i) incrementally increasing said delay;
      
      ii) comparing a voice to noise signal ratio at said increased delay with a previous voice to noise signal ratio to determine if said voice to noise signal ratio is increased; and
      
      , iii) repeating steps i) and ii) until said voice to noise signal ratio is determined not to have increased.
  - 17. A method as in claim 13 wherein the step c) of comparing said voice baseline with said noise baseline comprises the steps of:
    - i) incrementally decreasing said delay;
      
      ii) comparing a voice to noise signal ratio at said increased delay with a previous voice to noise signal ratio to determine if said voice to noise signal ratio is increased; and
      
      , iii) repeating steps i) and ii) until said voice to noise signal ratio is determined not to have increased.

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Current Assignee
Enterprise Systems Technologies S.a.r.l. (Atos SE)
Original Assignee
Siemens Information
Inventors
Slagle, Thomas D., Gartner, Martin

Granted Patent

US 6,785,381 B2
Time in Patent Office

Days
Field of Search
US Class Current

379/387.01
CPC Class Codes

H04M 1/6033 for providing handsfree use...

Telephone having improved hands free operation audio quality and method of operation thereof

First Claim

8 Assignments

0 Petitions

Accused Products

Abstract

50 Citations

17 Claims

Specification

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Telephone having improved hands free operation audio quality and method of operation thereof

First Claim

8 Assignments

Subscription Required

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0 Petitions

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Accused Products

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Abstract

50 Citations

17 Claims

Specification

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Solutions

Use Cases

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