LOW-POWER VOICE GATE FOR DEVICE WAKE-UP

• US 20140358552A1
• Filed: 05/31/2013
• Published: 12/04/2014
• Est. Priority Date: 05/31/2013
• Status: Abandoned Application

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Xu, Jefferson L.
• Application Number:
  US13/907,679
• Publication Number:
  US 20140358552A1
• Time in Patent Office: Days
• US Class Current: 704/275
• CPC Class Codes: G06F 1/3215 Monitoring of peripheral devices
• CPC Class Codes: G06F 1/3231 Monitoring the presence, absence or movement of users
• CPC Class Codes: G10L 2025/783 based on threshold decision
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A staged processing system may be configured to reduce power consumption during voice detection in an audio signal. A first stage may include detecting a minimal threshold of sound in an audio signal. A second stage may then be activated to apply a Teager operator to determine a signal-to-noise ratio of speech energy in an audio signal. When a minimum SNR is detected, a third stage may be activated to detect periodicity in the audio signal and identify a voice signal in the audio signal. When a voice signal is detected, a fourth stage may be activated to process the voice command.

Claims

1. A method, comprising:

receiving, at a processor, an audio signal;

applying, at the processor, a Teager operator to the audio signal to calculate an instantaneous change of energy in the audio signal;

calculating, at the processor, a signal-to-noise ratio (SNR) of the audio signal based, at least in part, on the calculated instantaneous change of energy; and

when the SNR is above a signal threshold, setting a first detection flag.

2. The method of claim 1, further comprising:

when the first detection flag is set;

calculating a peakness based on a cepstrum of the audio signal; and

when the peakness is above a threshold, setting a second detection flag.

3. The method of claim 2, further comprising when the second detection flag is set, waking a second processor for recognizing speech commands in the audio signal.

4. The method of claim 1, in which the step of calculating comprises calculating the instantaneous change of energy for a search window within the audio signal, and the step of calculating the SNR of the audio signal comprises computing a noise level based on a minimum energy value within the search window.

5. The method of claim 1, further comprising adjusting the signal threshold by estimating environmental fluctuations.

6. The method of claim 5, in which the step of calculating the threshold comprises classifying the environmental fluctuations based on at least one of a mean energy value of the audio signal and a standard deviation of the audio signal.

7. The method of claim 6, further comprising:

setting noise tracking coefficients for classifying the environmental fluctuation; and

adjusting the noise tracking coefficients.

8. The method of claim 1, in which the processor is an analog-to-digital converter (ADC).

9. An apparatus, comprising:

an audio signal input; and

a voice gate coupled to the audio signal input, the voice gate comprising;

a speech energy detection module configured to apply a Teager operator to an audio signal to calculate an instantaneous change of energy of the audio signal input and for calculating a signal-to-noise ratio (SNR) of the audio signal based, at least in part, on the calculated instantaneous change of energy; and

a detection flag output, in which the detection flag output is set when the SNR is above a signal threshold.

10. The apparatus of claim 9, further comprising a buffer coupled to the audio signal input, in which the buffer is configured to buffer incoming audio from the audio signal input.

11. The apparatus of claim 9, further comprising a decimation filter coupled to the voice gate and to the audio signal input, the decimation filter configured to reduce a sampling rate of audio samples from the audio signal input.

12. The apparatus of claim 9, further comprising:

an audio sample processing module coupled to the voice gate, in which the audio sample processing module is configured to power down the voice gate when the signal level is below a wake-up threshold; and

an analog-to-digital converter coupled to the audio signal input and to the voice gate, in which the analog-to-digital converter is configured to convert an analog signal from the audio signal input to a digital signal when the signal level is above the wake-up threshold.

13. The apparatus of claim 9, in which the speech energy detector is further configured to adjust the signal threshold based, at least in part, on an environmental fluctuation.

14. The apparatus of claim 9, in which the voice gate further comprises a voiced signal detection module coupled to the detection flag output, in which the voiced signal detection module is configured to:

calculate a peakness based on a cepstrum of the audio signal; and

when the peakness is above a threshold, generate a wake-up signal.

15. The apparatus of claim 14, further comprising an application processor coupled to the voice gate, in which the application processor is configured to further process the audio signal to determine a voice command in the audio signal, when the wake-up signal is generated.

16. A computer program product, comprising:

a non-transitory computer readable medium comprising code to perform the steps comprising;

receiving, at a processor, an audio signal;

applying, at the processor, a Teager operator to the audio signal to calculate an instantaneous change of energy in the audio signal;

calculating, at the processor, a signal-to-noise ratio (SNR) of the audio signal based, at least in part, on the calculated instantaneous change of energy; and

when the SNR is above a signal threshold, setting a first detection flag.

17. The computer program product of claim 16, in which the medium further comprises code to perform the steps of:

when the first detection flag is set, calculating a peakness based on a cepstrum of the audio signal; and

when the peakness is above a threshold, setting a second detection flag.

18. The computer program product of claim 17, in which the medium further comprises code to perform the step of, when the second detection flag is set, waking a second processor for recognizing speech commands in the audio signal.

19. The computer program product of claim 16, in which the medium further comprises code to perform the step of adjusting the signal threshold by estimating environmental fluctuations.

20. The computer program product of claim 16, in which the medium further comprises code to perform the steps of:

calculating the instantaneous change of energy for a search window within the audio signal; and

computing a noise level based on a minimum energy value within the search window.