Voice activity detector for audio signals

• US 10,418,052 B2
• Filed: 10/12/2017
• Issued: 09/17/2019
• Est. Priority Date: 02/26/2007
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Muesch, Hannes
• Primary Examiner(s): Godbold, Douglas
• Application Number:
  US15/730,908
• Publication Number:
  US 20180033453A1
• Time in Patent Office: 705 Days
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G10L 2025/932 Decision in previous or following frames
• CPC Class Codes: G10L 2025/937 Signal energy in various frequency bands
• 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 21/0364 for improving intelligibility
• 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: G10L 25/93 Discriminating between voiced and unvoiced parts of speech signals G10L25/90 takes precedence

Abstract

According to one aspect, a method for detecting voice activity is disclosed, the method including receiving a frame of an input audio signal, the input audio signal having an sample rate; dividing the frame into a plurality of subbands based on the sample rate, the plurality of subbands including at least a lowest subband and a highest subband; filtering the lowest subband with a moving average filter to reduce an energy of the lowest subband; estimating a noise level for each of the plurality of subbands; calculating a signal to noise ratio value for each of the plurality of subbands; and determining a speech activity level of the frame based on an average of the calculated signal to noise ratio values and a weighted average of an energy of each of the plurality of subbands. Other aspects include audio decoders that decode audio that was encoded using the methods described herein.

Claims

1. A method for determining voice activity in an audio signal, the method comprising:

receiving a frame of an input audio signal, the input audio signal having a sample rate;

spitting the audio signal into a plurality of subbands by way of a sequence of filter banks, the plurality of subbands including at least a lowest subband and a highest subband;

filtering the lowest subband with a linear filter to reduce an energy of the lowest subband;

estimating a noise level for at least some of the plurality of subbands such that in each subband, a noise level estimator tracks the background noise level and a Signal-to-Noise Ratio (SNR) value

calculating a signal to noise ratio value for at least some of the plurality of subbands; and

determining a speech activity level based at least in part on an average of the calculated signal to noise ratio values and an average of an energy of at least some of the plurality of subbands,

wherein the method is performed with one or more computing devices.

2. The method of claim 1 further comprising smoothing the calculated signal to noise ratio values over time to create temporally smoothed subband signal to noise values.

3. The method of claim 1 further comprising determining a weighted average of the calculated signal to noise ratio values as a spectral tilt of the frame.

4. The method of claim 1, wherein the SNR value is computed as a logarithm of the ratio of energy-to-noise level.