SYSTEMS, METHODS, APPARATUS, AND COMPUTER-READABLE MEDIA FOR GENERATING OBFUSCATED SPEECH SIGNAL

• US 20140006017A1
• Filed: 02/28/2013
• Published: 01/02/2014
• Est. Priority Date: 06/29/2012
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sen, Dipanjan
• Application Number:
  US13/780,233
• Publication Number:
  US 20140006017A1
• Time in Patent Office: Days
• US Class Current: 704/208
• CPC Class Codes: G10K 11/1754 Speech masking
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 21/003 Changing voice quality, e.g. pitch or formants
• CPC Class Codes: G10L 21/06 Transformation of speech into a non-audible representation, e.g. speech visualisation or speech processing for tactile aids G10L15/26 takes precedence
• CPC Class Codes: G10L 25/48 specially adapted for particular use
• CPC Class Codes: H04K 1/02 by adding a second signal to make the desired signal unintelligible
• CPC Class Codes: H04K 1/10 by using two signals transmitted simultaneously or successively
• CPC Class Codes: H04K 2203/12 for acoustic communication
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/42 characterized by the control of the jamming frequency or wavelength
• CPC Class Codes: H04K 3/825 by jamming
• CPC Class Codes: H04R 1/403 loud-speakers
• CPC Class Codes: H04R 2201/403 Linear arrays of transducers
• CPC Class Codes: H04R 2203/12 Beamforming aspects for stereophonic sound reproduction with loudspeaker arrays
• CPC Class Codes: H04R 3/12 for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04S 2400/11 Positioning of individual sound objects, e.g. moving airplane, within a sound field H04S2420/13 takes precedence
• CPC Class Codes: H04S 7/30 Control circuits for electronic adaptation of the sound field

Abstract

Arrangements are described that may be used to reduce the intelligibility of speech using masker signals which are obfuscated yet correlated versions of the speech. Other applications of pitch analysis and demodulation are also described. A system may be used to drive an array of loudspeakers to produce a sound field that includes a source component, whose energy is concentrated along a first direction relative to the array, and a masking component that is based on an estimated intensity of the source component in a second direction that is different from the first direction.

Claims

1. A method of signal processing, said method comprising:

producing a multichannel source signal that is based on a speech signal;

producing an obfuscated speech signal that is based on the speech signal;

producing a multichannel masking signal that is based on the obfuscated speech signal; and

driving a directionally controllable transducer, in response to the multichannel source signal and the multichannel masking signal, to produce a sound field comprising (A) a source component that is based on the multichannel source signal and (B) a masking component that is based on the multichannel masking signal.

2. The method according to claim 1, wherein said producing an obfuscated speech signal comprises, for each of a plurality of frames of the speech signal and for each of a plurality of different frequencies:

calculating an envelope of the frame at the frequency;

filtering the calculated envelope to obtain a filtered envelope; and

applying the filtered envelope to a carrier signal at the frequency to obtain a modulated carrier signal, and

wherein said producing an obfuscated speech signal comprises, for each of said plurality of frames of the speech signal, producing a corresponding frame of the obfuscated speech signal by combining the corresponding plurality of modulated carrier signals.

3. The method according to claim 2, wherein, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, said calculating the envelope of the frame at the frequency comprises applying, to the frame, a narrowband filter at the frequency.

4. The method according to claim 2, wherein, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, said calculated envelope is a complex envelope.

5. The method according to claim 2, wherein, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, said filtering the calculated envelope comprises applying a lowpass filter to the calculated envelope to obtain the filtered envelope.

6. The method according to claim 2, wherein an order in time of said corresponding frames of the obfuscated speech signal within the obfuscated speech signal is the same as an order in time of said plurality of frames of the speech signal within the speech signal.

7. The method according to claim 2, wherein each of said plurality of different frequencies is a harmonic of a pitch frequency of the speech signal.

8. The method according to claim 2, wherein said method comprises interpolating between estimates of a pitch frequency of the speech signal to obtain a pitch track of the speech signal, and wherein said plurality of different frequencies is based on said obtained pitch track.

9. The method according to claim 8, wherein said speech signal is based on an encoded signal that includes a plurality of pitch lag values, and wherein said pitch track is based on said plurality of pitch lag values.

10. The method according to claim 1, wherein energy of the source component is concentrated along a source direction relative to an axis of the transducer, and

wherein energy of the masking component is concentrated along a leakage direction, relative to said axis, that is different than the source direction.

11. The method according to claim 10, wherein said multichannel masking signal is based on an estimated intensity of the source component in the leakage direction.

12. The method according to claim 11, wherein said producing the multichannel source signal comprises applying a spatially directive filter to the speech signal to produce the multichannel source signal, and

wherein said estimated intensity of the source component in the leakage direction is based on coefficient values of the spatially directive filter.

13. The method according to claim 1, wherein said method comprises estimating a direction of a user relative to the directionally controllable transducer, and wherein said source direction is based on said estimated user direction.

14. The method according to claim 1, wherein the masking component includes a null in the source direction.

15. An apparatus for signal processing, said apparatus comprising:

means for producing a multichannel source signal that is based on a speech signal;

means for producing an obfuscated speech signal that is based on the speech signal;

means for producing a multichannel masking signal that is based on the obfuscated speech signal; and

means for driving a directionally controllable transducer, in response to the multichannel source signal and the multichannel masking signal, to produce a sound field comprising (A) a source component that is based on the multichannel source signal and (B) a masking component that is based on the multichannel masking signal.

16. The apparatus according to claim 15, wherein said means for producing an obfuscated speech signal comprises:

means for calculating, for each of a plurality of frames of the speech signal and for each of a plurality of different frequencies, an envelope of the frame at the frequency;

means for filtering, for each of the plurality of frames of the speech signal, each of said calculated envelopes to obtain a corresponding filtered envelope of a plurality of filtered envelopes;

means for applying, for each of the plurality of frames of the speech signal, each of the plurality of filtered envelopes to a carrier signal at the corresponding frequency to obtain a corresponding modulated carrier signal of a plurality of modulated carrier signals; and

means for producing, for each of said plurality of frames of the speech signal, a corresponding frame of the obfuscated speech signal by combining the corresponding plurality of modulated carrier signals.

17. The apparatus according to claim 16, wherein said means for calculating, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, the envelope of the frame at the frequency comprises means for applying, to each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, a narrowband filter at the frequency.

18. The apparatus according to claim 16, wherein, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, said calculated envelope is a complex envelope.

19. The apparatus according to claim 16, wherein said means for filtering, for each of said plurality of frames of the speech signal, each of said calculated envelopes comprises means for applying, for each of said plurality of frames of the speech signal, a lowpass filter to each of said calculated envelopes to obtain the corresponding filtered envelope.

20. The apparatus according to claim 16, wherein an order in time of said corresponding frames of the obfuscated speech signal within the obfuscated speech signal is the same as an order in time of said plurality of frames of the speech signal within the speech signal.

21. The apparatus according to claim 16, wherein each of said plurality of different frequencies is a harmonic of a pitch frequency of the speech signal.

22. The apparatus according to claim 16, wherein said apparatus comprises means for interpolating between estimates of a pitch frequency of the speech signal to obtain a pitch track of the speech signal, and wherein said plurality of different frequencies is based on said obtained pitch track.

23. The apparatus according to claim 22, wherein said speech signal is based on an encoded signal that includes a plurality of pitch lag values, and wherein said pitch track is based on said plurality of pitch lag values.

24. The apparatus according to claim 15, wherein energy of the source component is concentrated along a source direction relative to an axis of the transducer, and

wherein energy of the masking component is concentrated along a leakage direction, relative to said axis, that is different than the source direction.

25. The apparatus according to claim 24, wherein said multichannel masking signal is based on an estimated intensity of the source component in the leakage direction.

26. The apparatus according to claim 25, wherein said means for producing the multichannel source signal comprises means for applying a spatially directive filter to the speech signal to produce the multichannel source signal, and

wherein said estimated intensity of the source component in the leakage direction is based on coefficient values of the spatially directive filter.

27. The apparatus according to claim 15, wherein said apparatus comprises means for estimating a direction of a user relative to the directionally controllable transducer, and

wherein said source direction is based on said estimated user direction.

28. The apparatus according to claim 15, wherein the masking component includes a null in the source direction.

29. An apparatus for signal processing, said apparatus comprising:

a first spatially directive filter configured to produce a multichannel source signal that is based on a speech signal;

a masking signal generator configured to produce an obfuscated speech signal that is based on the speech signal;

a second spatially directive filter configured to produce a multichannel masking signal that is based on the obfuscated speech signal; and

an audio output stage configured to drive a directionally controllable transducer, in response to the multichannel source signal and the multichannel masking signal, to produce a sound field comprising (A) a source component that is based on the multichannel source signal and (B) a masking component that is based on the multichannel masking signal.

30. The apparatus according to claim 29, wherein said masking signal generator comprises:

an envelope calculator configured to calculate, for each of a plurality of frames of the speech signal and for each of a plurality of different frequencies, an envelope of the frame at the frequency;

a filter bank arranged to filter, for each of the plurality of frames of the speech signal, each of said calculated envelopes to obtain a corresponding filtered envelope of a plurality of filtered envelopes;

a modulator configured to apply, for each of the plurality of frames of the speech signal, each of the plurality of filtered envelopes to a carrier signal at the corresponding frequency to obtain a corresponding modulated carrier signal of a plurality of modulated carrier signals; and

a combiner configured to produce, for each of the plurality of frames of the speech signal, a corresponding frame of the obfuscated speech signal by combining the corresponding plurality of modulated carrier signals.

31. The apparatus according to claim 30, wherein said envelope calculator is configured to apply, to each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, a narrowband filter at the frequency.

32. The apparatus according to claim 30, wherein, for each of said plurality of frames of the speech signal and for each of said plurality of different frequencies, said calculated envelope is a complex envelope.

33. The apparatus according to claim 30, wherein said filter bank is configured to apply, for each of said plurality of frames of the speech signal, a lowpass filter to each of said calculated envelopes to obtain the corresponding filtered envelope.

34. The apparatus according to claim 30, wherein an order in time of said corresponding frames of the obfuscated speech signal within the obfuscated speech signal is the same as an order in time of said plurality of frames of the speech signal within the speech signal.

35. The apparatus according to claim 30, wherein each of said plurality of different frequencies is a harmonic of a pitch frequency of the speech signal.

36. The apparatus according to claim 30, wherein said apparatus comprises an interpolator configured to interpolate between estimates of a pitch frequency of the speech signal to obtain a pitch track of the speech signal, and wherein said plurality of different frequencies is based on said obtained pitch track.

37. The apparatus according to claim 36, wherein said speech signal is based on an encoded signal that includes a plurality of pitch lag values, and wherein said pitch track is based on said plurality of pitch lag values.

38. The apparatus according to claim 29, wherein energy of the source component is concentrated along a source direction relative to an axis of the transducer, and

wherein energy of the masking component is concentrated along a leakage direction, relative to said axis, that is different than the source direction.

39. The apparatus according to claim 38, wherein said multichannel masking signal is based on an estimated intensity of the source component in the leakage direction.

40. The apparatus according to claim 39, wherein said estimated intensity of the source component in the leakage direction is based on coefficient values of the first spatially directive filter.

41. The apparatus according to claim 29, wherein said apparatus comprises a direction-of-arrival estimator configured to estimate a direction of a user relative to the directionally controllable transducer, and

wherein said source direction is based on said estimated user direction.

42. The apparatus according to claim 29, wherein the masking component includes a null in the source direction.

43. A non-transitory computer-readable data storage medium having tangible features that cause a machine reading the features to:

produce a multichannel source signal that is based on a speech signal;

produce an obfuscated speech signal that is based on the speech signal;

produce a multichannel masking signal that is based on the obfuscated speech signal; and

drive a directionally controllable transducer, in response to the multichannel source signal and the multichannel masking signal, to produce a sound field comprising (A) a source component that is based on the multichannel source signal and (B) a masking component that is based on the multichannel masking signal.