Method for detecting a voice activity decision (voice activity detector)

• US 20030078770A1
• Filed: 10/25/2002
• Published: 04/24/2003
• Est. Priority Date: 04/28/2000
• Status: Active Grant

• Current Assignee: Deutsche Telekom AG
• Original Assignee: Deutsche Telekom AG
• Inventors: Erdmann, Christoph, Fischer, Alexander Kyrill
• Granted Patent: US 7,254,532 B2
• Time in Patent Office: Days
• US Class Current: 704/214
• 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

Abstract

The invention relates to a method for determining voice activity in a signal section of an audio signal. The result, i.e. whether voice activity is present in the section of the signal thus observed, depends upon spectral and temporal stationarity of the signal section and/or prior signal sections. In a first step, the method determines whether there is spectral stationatity in the observed signal section. In a second step, the method determines whether there is temporal stationarity in the signal section in question. The final decision as to the presence of voice activity in the signal section observed depends upon the initial values of both steps.

Claims

1. A method for determining speech activity in a signal segment of an audio signal, the result of whether speech activity is present in the observed signal segment depending both on the spectral and on the temporal stationarity of the signal segment and/or on preceding signal segments,

wherein in a first stage, the method assesses whether spectral stationarity is present in the observed signal segment;

and

in a second stage, it is assessed whether temporal stationarity is present in the observed signal segment, the final decision on the presence of speech activity in the observed signal segment being dependent on the output values of the two stages.

2. The method as recited in claim 1,

wherein for determining the spectral stationarity and the energy change (temporal stationarity) at least one temporally preceding signal segment is taken into account.

3. The method as recited in one of the preceding claims,

wherein each signal segment is divided into at least two subsegments which can overlap, the speech activity being determined for each subsegment.

4. The method as recited in claim 3,

wherein for assessing the speech activity of a temporally subsequent signal segment, the determined values for the speech activity of the individual subsegments of each preceding signal segment are taken into account.

5. The method as recited in one of the preceding claims,

wherein in the first stage, the spectral distortion between the currently observed signal segment and the preceding signal segment or signal segments is determined.

6. The method as recited in one of the preceding claims,

wherein the first stage makes a decision on the stationarity of the observed signal segment, it being possible for an output variable STAT1 to take the values “

stationary”

or “

non-stationary”

.

7. The method as recited in claim 6,

wherein the decision on the stationarity is made on the basis of the previously determined linear prediction coefficients of the current signal segment LPC_NOW and of a previously determined measure for the voicedness of the observed signal segment.

8. The method as recited in claim 7,

wherein in addition, the number of signal segments N_INSTAT2 which have been classified as “

non-stationary”

by the second stage in the analysis of the preceding signal segments are taken into account for the assessment of STAT1.

9. The method as recited in claim 7 or 8,

wherein in addition, values computed for the preceding frames, such as STIMM_MEM[0 . . . 1], LPC_STAT1, are taken into account in the calculation of a value for STAT1.

10. The method as recited in one of the preceding claims,

wherein in addition to the output value STAT1, the first stage produces a further output value LPC_STAT1 which is dependent on LPC_NOW and STAT1.

11. The method as recited in one of the preceding claims,

wherein for assessing whether temporal stationarity is present, at least the following input variables are used in the second stage:

signal segment in sampled form;

STAT1 (decision of the first stage).

12. The method as recited in claim 11,

wherein, in addition, the following input variables are used in the second stage:

the linear prediction coefficients LPC_STAT1 describing the last stationary signal segment;

the energy E_RES_REF of the residual signal of the previous stationary signal segment;

a variable START which controls a restart of the value adaptation, it being possible for the variable START to take the values “

true” and

“

false”

.

13. The method as recited in one of the preceding claims,

wherein the second stage outputs “

stationary”

as the result for STAT2 each time that STAT1 is equal to “

stationary”

.

14. The method as recited in one of the preceding claims,

wherein the value of STAT2 is the measure for the speech activity of the observed signal segment.