High frequency compression integration

• US 8,249,861 B2
• Filed: 12/22/2006
• Issued: 08/21/2012
• Est. Priority Date: 04/20/2005
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: QNX Software Systems Limited (Canada) (Blackberry Limited)
• Inventors: Li, Xueman, Hetherington, Phillip, Escott, Alex
• Primary Examiner(s): He, Jialong
• Application Number:
  US11/645,079
• Publication Number:
  US 20070174050A1
• Time in Patent Office: 2,069 Days
• Field of Search: 704/205, 704/208, 704/201, 704/206, 704/225, 381/316, 381/321
• US Class Current: 704/205
• 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: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: G10L 21/0264 characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

A speech enhancement system that improves the intelligibility and the perceived quality of processed speech includes a frequency transformer and a spectral compressor. The frequency transformer converts speech signals from the time domain to the frequency domain. The spectral compressor compresses a pre-selected portion of the high frequency band and maps the compressed high frequency band to a lower band limited frequency range. The speech enhancement system may be built into, may be a unitary part of, or may be configured to interface other systems that process audio or high frequency signals.

Claims

1. A speech system that improves the intelligibility and quality of a processed speech, comprising:

a first spectral compressor that compresses a first pre-selected high frequency band and maps the first compressed high frequency band to a first band limited lower frequency range;

an acoustic echo canceller coupled with an output of the first spectral compressor to receive a first sound signal modified by the first spectral compressor, where the acoustic echo canceller dampens repetitive sounds in the first sound signal created by a reflection from a surface; and

a second spectral compressor coupled with an output of the acoustic echo canceller to receive a second sound signal modified by the acoustic echo canceller, where the second spectral compressor compresses a second pre-selected high frequency band of the second sound signal and maps the second compressed high frequency band to a second lower band limited frequency range, and where the second spectral compressor comprises circuitry or a computer-readable storage medium that stores instructions executable by a processor.

2. The system of claim 1, further comprising a frequency converter coupled with the first spectral compressor or the second spectral compressor, where the frequency converter is programmed to automatically convert a speech signal into its frequency spectrum in nearly real time.

3. The system of claim 1, further comprising a frequency converter coupled with the first spectral compressor or the second spectral compressor, where the frequency converter is programmed or configured to automatically convert a speech signal into a spectrum of frequencies in real time.

4. The system of claim 1, where the first high frequency band comprises a larger range of frequencies than the first lower band limited frequency range.

5. The system of claim 1 where the first spectral compressor or the second spectral compressor comprises a non-linear compression basis function, and where the acoustic echo canceller comprises a device that dampens the repetitive sounds.

6. The system of claim 1 where the second lower band limited frequency range comprises a portion of an analog bandwidth.

7. The system of claim 1 where the second lower band limited frequency range comprises a portion of a telephone bandwidth.

8. The system of claim 1 further comprising a noise detector configured to detect and measure a level of noise present in a speech signal received at an input of the first spectral compressor or the second spectral compressor.

9. The speech system of claim 8, further comprising a gain controller configured to apply a variable gain to the first compressed high frequency band or the second compressed high frequency band, where the gain controller is configured to select a level for the variable gain based on the measured level of noise present in the speech signal.

10. The system of claim 1 further comprising a noise detector configured to detect and estimate a level of noise present when a speech signal is detected.

11. The system of claim 1 further comprising a gain controller configured to adjust a gain of the first compressed high frequency band or the second compressed high frequency band in relation to an independent extraneous signal.

12. The system of claim 11 where the independent extraneous signal comprises a background noise.

13. The system of claim 1 further comprising a gain controller coupled to the first spectral compressor, where the gain controller is configured to adjust only the gain of the first compressed high frequency band at the first lower band limited frequency range.

14. The system of claim 13 where the gain controller is configured to apply a plurality of gain adjustments that varies with a signal independent of a detected speech signal.

15. The speech system of claim 1, where the first lower band limited frequency range is different than the second lower band limited frequency range.

16. The speech system of claim 1, further comprising a gain controller configured to adjust a gain of the first compressed high frequency band or the second compressed high frequency band, and where the gain controller is configured to select a level for the gain based on a change in power level in the first compressed high frequency band or the second compressed high frequency band due to the compression of the first pre-selected high frequency band or the second pre-selected high frequency band into the first lower band limited frequency band or the second lower band limited frequency band.

17. The speech system of claim 1, further comprising a gain controller configured to adjust a gain of the first compressed high frequency band or the second compressed high frequency band, and where the gain controller is configured to select a level for the gain that substantially aligns a slope of a noise floor present in the first compressed high frequency band or the second compressed high frequency band with a slope of a noise floor present in an uncompressed frequency band.

18. A speech system that improves the intelligibility of a processed speech, comprising:

a high pass filter that passes frequencies above a first frequency;

a low pass filter in communication with the high pass filter that passes frequencies below a second frequency;

an acoustic echo canceller in communication with the lowpass filter that dampens repetitive sounds created by a reflection from a surface;

a mixer that combines an output of the acoustic echo canceller with an output of the high pass filter;

a frequency transformer that converts an output of the mixer into its frequency domain;

a spectral compressor coupled to the frequency transformer that compresses a pre-selected high frequency band of a first signal and maps the compressed high frequency band to a lower frequency band; and

a gain controller configured to adjust a gain of the compressed high frequency band proportionally to the changing level of an independent and extraneous signal, where the gain controller selects a level for the gain that changes across a frequency range of the compressed high frequency band based on a slope of a noise floor present in an uncompressed frequency band of the first signal and a slope of a noise floor present in the compressed high frequency band of the first signal, and where the gain controller comprises circuitry or a computer-readable storage medium that stores instructions executable by a processor.

19. The speech system of claim 18 further comprising a controller that regulates the spectral compressor, the controller comprising a monitor that compares a signal-to-noise ratio of the compressed signal to a signal-to-noise ratio of the signal before it is compressed.

20. The speech system of claim 18 where the gain controller is configured to apply a gain that varies with a changing level of the extraneous signal.

21. The speech system of claim 18 further comprising a beamformer in communication with the gain controller that increases a gain of a desired range of signals while lowering a gain of a signal traveling from an originating source of noise.

24. The speech system of claim 19 further comprising:

an additional frequency transformer that converts an output of the acoustic echo canceller into a frequency domain;

an additional noise detector configured to detect and estimate a second level of noise present in the output of the acoustic echo canceller; and

an additional gain controller configured to adjust the gain of the second compressed high frequency band proportionally to the second level of noise present in the output of the acoustic echo canceller.

22. A speech system that improves the intelligibility of a processed speech, comprising:

a plurality of devices that detect and convert sound waves into electrical signals;

a plurality of frequency transformers that convert an output of one of the plurality of devices into its frequency domain;

a plurality of first spectral compressors, each of the first spectral compressors being in communication with one of the plurality of frequency transformers, and each of the first spectral compressors being configured to compress a first pre-selected high frequency band and map the first compressed high frequency band to a first lower frequency band;

a plurality of noise detectors each configured to detect and estimate a level of noise present in at least one of the sound waves detected by the respective plurality of devices and compressed by the respective plurality of spectral compressors;

a plurality of gain controllers each configured to adjust a gain of at least one of the compressed high frequency bands proportionally to the level of noise present in at least one of the sound waves detected by the respective plurality of devices and compressed by the respective plurality of spectral compressors;

a beamformer configured to receive signals processed by the plurality of first spectral compressors and the plurality of gain controllers;

an acoustic echo canceller configured to receive an output signal of the beamformer; and

a second spectral compressor configured to receive an output signal of the acoustic echo canceller, compress a second pre-selected high frequency band of the output signal of the acoustic echo canceller, and map the second compressed high frequency band to a second lower frequency band.

23. The speech system of claim 22 further comprising a plurality of frequency to time transformers each in communication with at least one of the plurality of gain controllers and the beamformer.

25. The speech system of claim 22, where at least one of the plurality of spectral compressors comprises circuitry or a computer-readable storage medium that stores instructions executable by a processor.

26. A speech system that improves the intelligibility of a processed speech, comprising:

a beamformer that passes selected audio signals received from a plurality of receivers;

a frequency transformer that converts speech signals from time domain into frequency domain in real time;

a spectral compressor coupled to the frequency transformer that compresses a pre-selected high frequency band of a signal and maps the compressed high frequency band to a lower frequency band within a telephone pass band;

a noise detector configured to detect and measure a background noise level of speech signals; and

a gain controller configured to apply a variable gain to the compressed high frequency band in relation to the level of the background noise, where the gain controller is configured to select a level for the variable gain that substantially aligns a slope of a noise floor present in the compressed high frequency band of the signal with a slope of a noise floor present in an uncompressed frequency band of the signal, where the gain controller comprises circuitry or a computer-readable storage medium that stores instructions executable by a processor.

27. The speech system of claim 26 further comprising a controller that regulates the spectral compressor through a communication bus, the controller compares a signal-to-noise ratio of a portion of the detected speech signal to a signal-to-noise ratio of a portion of the compressed signal.

28. The speech system of claim 27 where the controller is programmed to compare amplitude through a comparison of frequency bins.

29. The speech system of claim 27 further comprising an automatic speech recognition system coupled to the gain controller.