Cardioid beam with a desired null based acoustic devices, systems and methods

• US 7,386,135 B2
• Filed: 07/26/2002
• Issued: 06/10/2008
• Est. Priority Date: 08/01/2001
• Status: Active Grant

• Current Assignee: Solos Technology Limited
• Original Assignee: Dashen Fan
• Inventors: Fan, Dashen
• Primary Examiner(s): Chin, Vivian
• Assistant Examiner(s): Faulk, Devona E
• Application Number:
  US10/206,242
• Publication Number:
  US 20050074129A1
• Time in Patent Office: 2,146 Days
• Field of Search: 381/92, 381/56, 381/111, 381/122, 381/71.1, 381 941- 949
• US Class Current: 381/92
• CPC Class Codes: G10L 15/20 Speech recognition techniques specially adapted for robustness in adverse environments, e.g. in noise, of stress induced speech G10L21/02 takes precedence
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 2021/02161 Number of inputs available containing the signal or the noise to be suppressed
• CPC Class Codes: G10L 2021/02165 Two microphones, one receiving mainly the noise signal and the other one mainly the speech signal
• CPC Class Codes: H04R 2410/01 Noise reduction using microphones having different directional characteristics
• CPC Class Codes: H04R 2410/05 Noise reduction with a separate noise microphone
• CPC Class Codes: H04R 25/407 Circuits for combining signals of a plurality of transducers
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

An acoustic device is provided with first and second one or more acoustic elements to generate a first signal that includes mostly undesired audio and substantially void of desired audio, and a second signal that includes desired as well undesired audio respectively. The first one or more acoustic elements are designed and arranged to generate a Cardioid beam with a null at an originating direction of the desired audio. The second one or more acoustic elements are designed and arranged to generate a complementary beam that includes the desired audio. A system is provided with an appropriate signal processing logic to recover the desired audio using the first and second signals. The signal processing logic may practice echo cancellation like techniques or blind signal separation techniques.

Claims

1. A system, comprising:

an acoustic device having a plurality of acoustic elements designed and arranged to facilitate generation of a first signal that includes mostly undesired audio, substantially void of desired audio;

a second signal that includes both the desired and the undesired audio; and

a signal processing subsystem coupled to the acoustic device to extract the desired audio using the first and second signals;

wherein said signal processing subsystem comprises a signal separation component eguipped to subtract the first signal from the second signal;

wherein said signal processing subsystem further comprises a delay component to introduce a deterministic delay to said second signal;

wherein said signal separation component comprises logic to employ an echo cancellation like technique to subtract the first signal from the second signal;

wherein said signal processing subsystem further comprises an inhibit component to inhibit said signal separation component from performing at least one of signal filtering and adapting filtering; and

wherein said signal processing subsystem further comprises a plurality of mean amplitude estimators and a comparator coupled to each other and to said inhibit component to provide said inhibit component with inputs for determining whether to inhibit said signal separation component from performing at least one of signal filtering and adapting filtering.

2. A system, comprising:

an acoustic device having a plurality of acoustic elements designed and arranged to facilitate generation of a first signal that includes mostly undesired audio, substantially void of desired audio,

a second signal that includes both the desired and the undesired audio; and

a signal processing subsystem coupled to the acoustic device to extracted the desired audio using the first and second signals;

wherein said signal processing subsystem comprises a signal separation component equipped to subtract the first signal from the second signal;

wherein said signal processing subsystem further comprises a delay component to introduce a deterministic delay to said second signal;

said signal separation component comprises logic to employ an echo cancellation like technique to subtract the first signal from the second signal; and

wherein said desired audio is desired speech, and said signal processing subsystem further comprises a first and a second pre-whitening component coupled to the delay and the signal separation component respectively, and a de-whitening component coupled to said signal separation component, to condition said first and second signals prior to extracting desired audio from the signals, and the re-condition the extracted desired audio.

3. A signal extraction method comprising:

generating a first signal that includes mostly undesired audio, substantially void of desired audio, and a second signal that includes both the desired and the undesired audio;

extracting the desired audio using the first and second signals;

wherein said extracting comprises subtracting the first signal from the second signal;

wherein said extracting further comprises introducing a deterministic delay to said second signal;

said subtracting comprises subtracting the first signal from the second signal employing an echo cancellation like technique;

wherein said echo cancellation like technique comprises performing a selected one of normalized time domain, freguency domain and sub-band least-mean-square adaptive filtering operations on the first and second signals;

wherein said method further comprises conditioning inhibiting at least one of said filtering and adapting said filtering; and

wherein the method further comprises computing mean amplitude estimations for the signals, comparing the estimated mean amplitudes, and providing the comparison results for said conditional inhibition.