Method and system for suppressing receiver audio regeneration

• US 7,280,958 B2
• Filed: 09/30/2005
• Issued: 10/09/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Pavlov, Peter M., McIntosh, Jason D., Johnson, Graeme P.
• Primary Examiner(s): Hudspeth; David
• Assistant Examiner(s): Ng; Eunice
• Application Number:
  US11/241,351
• Publication Number:
  US 20070078647A1
• Time in Patent Office: 739 Days
• Field of Search: 704/205, 704/207
• US Class Current: 704/207
• CPC Class Codes: G10L 21/013 Adapting to target pitch
• CPC Class Codes: G10L 21/02 Speech enhancement, e.g. noise reduction or echo cancellation reducing echo effects in line transmission systems H04B3/20; echo suppression in hands-free telephones H04M9/08
• CPC Class Codes: H04R 3/02 for preventing acoustic reaction , i.e. acoustic oscillatory feedback specially adapted for hearing aids H04R25/453

Abstract

The invention concerns a method (500) and system (100) for suppressing receiver audio regeneration. The method (500) includes the steps of receiving a communication signal (502), at a Radio Frequency (RF) unit (102), demodulating the communication signal to an audio signal (504), monitoring a volume level of the audio signal (506), and shifting the pitch of the audio signal when the volume level reaches a predetermined threshold (508), and playing the pitch-shifted audio signal out of a speaker to produce a pitch-shifted acoustic signal (510). The method can shift the pitch of the audio signal to produce a pitch-shifted acoustic signal with signal properties suppressing regeneration of the acoustic signal onto the audio signal at the RF unit. The amount of pitch-shifting can be a function of the volume level.

Claims

1. A method for suppressing receiver audio regeneration, comprising the steps of:

receiving a communication signal;

at a Radio Frequency (RF) unit, demodulating the communication signal to an audio signal;

monitoring a volume level of the audio signal;

shifting a pitch of the audio signal when the volume level reaches a predetermined threshold to produce a pitch shifted audio signal, wherein an amount of pitch-shifting of the audio signal is a function of the volume level; and

playing the pitch-shifted audio signal out of a speaker to produce a pitch-shifted acoustic signal;

wherein the amount of pitch-shifting applied to the audio signal produces a pitch-shifted acoustic signal with signal properties suppressing regeneration of the acoustic signal onto the audio signal at the RF unit.

2. The method according to claim 1, wherein the step of monitoring the volume level comprises the steps of:

estimating an acoustic signal volume for at least a portion of the time-based samples of the audio signal; and

based on the estimating step, generating a volume contour of the acoustic signal.

3. The method according to claim 2, wherein the pitch of the audio signal is shifted when the volume contour exceeds the predetermined threshold, wherein the amount of pitch-shifting of the audio signal is a function of the volume level of the acoustic signal.

4. The method according to claim 2, wherein the step of monitoring the volume level further comprises the steps of:

detecting speech activity on the audio signal; and

when detecting speech on the audio signal, determining whether the volume contour exceeds the predetermined threshold.

5. The method according to claim 4, wherein if no speech is detected on the audio signal, the method further comprises predicting the amount of pitch shift.

6. The method according to claim 1, wherein shifting the pitch can be done by one of increasing and decreasing the pitch of the audio signal, wherein the step of shifting the pitch can be on one of a linear and non-linear scale.

7. The method according to claim 1, wherein the amount of pitch shifting is within 20% of the audio signal.

8. The method according to claim 1, wherein the pitch-shifting of the audio signal suppresses the RF unit from entering unstable oscillation.

9. The method according to claim 1, further comprising the steps of:

evaluating a margin; and

updating the predetermined threshold level based on the margin, wherein the updating sets an allowable gain headroom;

wherein the margin can be one of a gain margin and phase margin that reveals an allowable extent of pitch shifting before unstable oscillation.

10. The method according to claim 1, wherein the demodulating the communication signal further comprises demodulating to an intermediate frequency signal, followed by demodulating the intermediate frequency signal to the audio signal.

11. A system for suppressing receiver audio regeneration, comprising:

a Radio Frequency (RF) unit to receive a communication signal, containing a demodulator, wherein the demodulator demodulates the communication signal to an audio signal having a volume level;

a pitch-shifter coupled to the demodulator, wherein the pitch-shifter shifts a pitch of the audio signal when the volume level reaches a predetermined threshold to produce a pitch-shifted audio signal, wherein the amount of pitch-shifting shifting is a function of the volume level; and

a speaker connected to the pitch shifter, wherein the speaker plays the pitch-shifted audio signal to produce a pitch-shifted acoustic signal;

wherein the pitch-shifter shifts the pitch of the audio signal by an amount that suppresses regeneration of an acoustic signal onto the audio signal at the RF unit.

12. The system according to claim 11, wherein the pitch shifter further comprises an analysis section that monitors a volume level of the audio signal, and when the volume level exceeds the predetermined threshold, the pitch-shifter shifts the pitch of the audio signal by an amount that is a function of the volume level of the acoustic signal.

13. The system according to claim 12, wherein the audio signal is comprised of a plurality of time-based samples and wherein the analysis section comprises:

a volume estimator block to estimate the acoustic signal volume for at least a portion of the time-based samples of the audio signal; and

an envelope module cooperatively connected to the volume estimator to generate a volume contour of the acoustic signal based on the volume estimation.

14. The system according to claim 12, wherein the analysis section further comprises:

a speech detector for detecting speech activity on the audio signal; and

a threshold unit cooperatively connected to the speech detector to determine when the volume contour exceeds the predetermined threshold, when the speech detector detects speech on the audio signal.

15. The system according to claim 11, wherein the pitch-shifter shifts the pitch of the audio signal by one of increasing and decreasing the pitch of the audio signal.

16. The system according to claim 11, wherein the pitch-shifter shifts the pitch of the audio signal up to 20%.

17. The system according to claim 11, wherein the pitch-shifter shifts the pitch of the audio signal to suppress unstable oscillation in the RF unit.

18. The system according to claim 11, wherein the pitch-shifter further comprises a stability unit to evaluate a margin, and, based on the margin, wherein the margin can be one of a gain margin and phase margin which reveals an allowable extent of pitch shifting before unstable oscillation, update the predetermined threshold to set an allowable gain headroom.

19. A machine readable storage medium, having stored thereon a computer program having a plurality of code sections executable by a portable computing device for causing the portable computing device to perform the steps of:

at a Radio Frequency (RF) unit, receiving a communication signal;

demodulating the communication signal into an audio signal;

monitoring a volume level of the audio signal;

shifting the pitch of the audio signal when the volume level reaches a predetermined threshold, wherein the amount of pitch-shifting is a function of the volume level; and

playing the pitch-shifted audio signal out of a speaker to produce a pitch-shifted acoustic signal;

wherein the pitch-shifting produces a pitch-shifted acoustic signal with signal properties suppressing regeneration of the acoustic signal onto the audio signal at the RF unit.

20. A system for suppressing receiver audio regeneration, comprising the steps of:

generating a volume contour for an acoustic signal;

monitoring the volume level of the volume contour; and

shifting the pitch of an audio signal when the volume level reaches a predetermined threshold;

wherein the pitch-shifter shifts the pitch of the audio signal to produce a pitch-shifted acoustic signal with signal properties suppressing regeneration of the acoustic signal onto the audio signal at a RF unit.