Multi-channel periodic signal enhancement system

• US 8,543,390 B2
• Filed: 08/31/2007
• Issued: 09/24/2013
• Est. Priority Date: 10/26/2004
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: QNX Software Systems Limited (Canada) (Blackberry Limited)
• Inventors: Nongpiur, Rajeev, Hetherington, Phillip
• Primary Examiner(s): Godbold, Douglas
• Application Number:
  US11/849,009
• Publication Number:
  US 20080019537A1
• Time in Patent Office: 2,216 Days
• Field of Search: 704200-201, 704226-227
• US Class Current: 704/226
• CPC Class Codes: G10L 21/0364 for improving intelligibility
• CPC Class Codes: G10L 25/90 Pitch determination of speech signals
• CPC Class Codes: H03H 21/0012 Digital adaptive filters
• CPC Class Codes: H03H 2220/08 Variable filter length

Abstract

A multi-channel signal enhancement system reinforces signal content and improves the signal-to-noise ratio of a multi-channel signal. The system detects, tracks, and reinforces non-stationary periodic signal components of a multi-channel signal. The periodic signal components of the signal may represent vowel sounds or other voiced sounds. The system may detect, track, or attenuate quasi-stationary signal components in the multi-channel signal.

Claims

1. A signal enhancement system having an audio source device configured to generate a plurality of input signals from a common source, the system comprising:

a plurality of periodic signal enhancement circuits implemented in hardware or executed by a processor, each periodic signal enhancement circuit comprising an adaptive filter and each periodic signal enhancement circuit configured to;

receive the respective input signal;

add a first periodic signal component in the input signal with a second periodic signal component in an output of the adaptive filter to increase the first periodic signal component in the input signal, the second periodic signal component being at least partially in-phase with the first periodic signal component; and

generate an enhanced output signal, the enhanced output signal comprising the increased first periodic signal component;

a plurality of alignment circuits, each configured to receive the respective enhanced output signal and a common reference signal;

the respective alignment circuit time-aligning each enhanced output signal with the common reference signal to generate a time-aligned output signal; and

a summing circuit configured to;

add the respective time-aligned output signals and the common reference signal to generate an enhanced time-aligned output signal; and

output the enhanced time-aligned output signal.

2. The system according to claim 1, where the common reference signal is selected from the respective enhanced output signals having a highest signal-to-noise ratio.

3. The system according to claim 1, where the plurality of input signals are generated by a common audio source and contain correlated signal components.

4. The system according to claim 1, where the audio source device comprises a microphone array.

5. The system according to claim 1, where the audio source device is selected from the group consisting of a microphone array, a directional microphone array, a plurality of directional microphones, a telecommunications network, or the Internet.

6. The system according to claim 1, where each alignment circuit includes an adaptive filter circuit having a plurality of coefficients.

7. The system according to claim 6, further comprising a multiplier circuit in each alignment circuit configured to scale an output of the adaptive filter circuit by a weighting factor.

8. The system according to claim 7, where a sum of the weighing factors is between about zero and about one.

9. The system according to claim 6, further comprising a delay circuit configured to delay the common reference signal so that the coefficients of the adaptive filter circuit peak at about a mid-point in the respective adaptive filter circuit.

10. The system according to claim 1, further comprising:

a selection circuit configured to calculate a signal-to-noise ratio for each enhanced output signal;

a comparison circuit configured to compare the calculated signal-to-noise ratio; and

a path selection circuit configured to select the enhanced output signal having a highest signal-to-noise ratio, and output the selected signal as the common reference signal.

11. The system according to claim 1, where each periodic signal enhancement circuit includes a reinforcement logic circuit.

12. The system according to claim 1, where respective alignment circuits apply a least-squares logic to time-align the enhanced output signal with the common reference signal.

13. The system according to claim 12, where the least-squares logic is selected from the group consisting of recursive least-squares, normalized least mean squares, proportional least mean squares, or least mean squares.

14. A signal enhancement system comprising:

an audio source device configured to generate a plurality of input signals from a common source, the input signals having correlated signal components;

a plurality of periodic signal enhancement circuits implemented in hardware or executed by a processor, each periodic signal enhancement circuit comprising an adaptive filter and each periodic signal enhancement circuit configured to;

receive the respective input signal;

add a first periodic signal component in the input signal with a second periodic signal component in an output of the adaptive filter to increase the first periodic signal component in the input signal, the second periodic signal component being at least partially in-phase with the first periodic signal component; and

generate an enhanced output signal, the enhanced output signal comprising the increased first periodic signal component;

a selection circuit configured to calculate a signal-to-noise ratio for each enhanced output signal and select an enhanced output signal having a highest signal-to-noise ratio as a common reference signal;

a plurality of alignment circuits, each configured to receive the respective enhanced output signal and the common reference signal;

the respective alignment circuit time-aligning each enhanced output signal with the common reference signal to generate a time-aligned output signal; and

a summing circuit configured to;

add the respective time-aligned output signals and the common reference signal to generate an enhanced time-aligned output signal; and

output the enhanced time-aligned output signal.

15. A signal enhancement system having an audio source device configured to generate a plurality of input signals from a common source, the system comprising:

a selection circuit configured to calculate a signal-to-noise ratio for each input signal and select an input signal having a highest signal-to-noise ratio as a common reference signal;

a periodic signal enhancement circuit implemented in hardware or executed by a processor, the periodic enhancement circuit comprising an adaptive filter and the periodic signal enhancement circuit configured to;

receive the common reference signal;

add a first periodic signal component in the common reference signal with a second periodic signal component in an output of the adaptive filter to increase the first periodic signal component in the common reference signal, the second periodic signal component being at least partially in-phase with the first periodic signal component; and

generate an enhanced common reference signal, the enhanced common reference signal comprising the increased first periodic signal component;

a plurality of alignment circuits, each configured to receive the respective input signal and the enhanced common reference signal, the respective alignment circuit time-aligning each input signal with the enhanced common reference signal to generate a time-aligned output signal; and

a summing circuit configured to;

add the respective time-aligned output signals and the enhanced common reference signal to generate an enhanced time-aligned output signal; and

output the enhanced time-aligned output signal.

16. A method for enhancing a signal, comprising:

receiving a plurality of input signals from an audio source device;

enhancing each of the input signals to generate respective enhanced output signals, where for each of the input signals, enhancing the input signal comprises;

adding a first periodic signal component in the input signal with a second periodic signal component in an output of the adaptive filter to increase the first periodic signal component in the input signal, the second periodic signal component being at least partially in-phase with the first periodic signal component, the enhanced output signal comprising the increased first periodic signal component;

aligning in time each of the enhanced output signals with a common reference signal to generate respective time-aligned output signals, the common reference signal based on an enhanced output signal having a highest signal-to-noise ratio; and

summing the respective time-aligned output signals and the common reference signal to generate an enhanced time-aligned output signal.

17. The method according to claim 16 further comprising generating the plurality of input signals by a common audio source, the input signals containing correlated signal components.

18. The method according to claim 16, further comprising providing the plurality of input signals using an array of transducers.

19. The method according to claim 16, further comprising adaptively filtering the respective enhanced output signals to time-align the respective enhanced output signal with the common reference signal.

20. The method according to claim 19, further comprising multiplying respective results of the adaptive filtering by a respective weighting factor.

21. The method according to claim 20, where a sum of the respective weighting factors is between about zero and about one.

22. The method according to claim 16, further comprising:

calculating an signal-to-noise ratio for each enhanced output signal;

comparing the calculated signal-to-noise ratio;

selecting an enhanced output signal having the highest signal-to-noise ratio; and

outputting the selected signal as the common reference signal.

23. The method according to claim 16, where enhancing each of the input signals comprises reinforcing signal components of the respective input signals.

24. The method according to claim 16, further comprising processing the respective enhanced output signals using a least-squares process to time-align the enhanced output signal with the common reference signal.

25. A non-transitory computer-readable storage medium comprising processor-executable instructions to enhance a multi-channel signal configured to:

receive a plurality of input signals from an audio source device;

enhance each of the input signals to generate respective enhanced output signals by adding a first periodic signal component in the input signal with a second periodic signal component in an output of the adaptive filter to increase the first periodic signal component in the input signal, the second periodic signal being at least partially in-phase with the second periodic signal component, each of the enhanced output signals comprising the increased first periodic signal component;

align in time each of the enhanced output signals with a common reference signal to generate respective time-aligned output signals, the common reference signal based on an enhanced output signal having a highest signal-to-noise ratio; and

sum the respective time-aligned output signals and the common reference signal to generate an enhanced time-aligned output signal.