Methods and apparatus for distinguishing stationary signals from non-stationary signals
First Claim
1. A method of distinguishing a stationary signal from a non-stationary signal, the method comprising:
- determining a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals including a current time interval;
averaging the LPC coefficients over a plurality of successive time intervals preceding the current time interval;
determining a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients;
declaring the signal to be stationary in the current time interval when the cross-correlation exceeds a threshold value; and
declaring the signal to be non-stationary in the current time interval when the cross-correlation is less than the threshold value.
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Abstract
In methods and apparatus for distinguishing stationary signals from non-stationary signals, a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals, including a current time interval, is determined. The LPC coefficients are averaged over a plurality of successive time intervals preceding the current time interval, and a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients is determined. The signal is declared to be stationary in the current time interval when the cross-correlation exceeds a threshold value, and is declared to be non-stationary in the current time interval when the cross-correlation is less than the threshold value. The methods and apparatus are particularly applicable to detection of transitions between an absence of speech state, characterized by a stationary signal, and a presence-of-speech state characterized by a non-stationary signal.
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Citations
23 Claims
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1. A method of distinguishing a stationary signal from a non-stationary signal, the method comprising:
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determining a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals including a current time interval; averaging the LPC coefficients over a plurality of successive time intervals preceding the current time interval; determining a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients; declaring the signal to be stationary in the current time interval when the cross-correlation exceeds a threshold value; and declaring the signal to be non-stationary in the current time interval when the cross-correlation is less than the threshold value. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for distinguishing a stationary signal from a non-stationary signal, the apparatus comprising a processor and a memory connected to the processor storing instructions for execution by the processor, the instructions comprising:
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instructions for determining a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals including a current time interval; instructions for averaging the LPC coefficients over a plurality of successive time intervals preceding the current time interval; instructions for determining a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients; instructions for declaring the signal to be stationary in the current time interval when the cross-correlation exceeds a threshold value; and instructions for declaring the signal to be non-stationary in the current time interval when the cross-correlation is less than the threshold value. - View Dependent Claims (7, 8, 9, 10)
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11. A processor-readable storage device storing instructions for distinguishing a stationary signal from a non-stationary signal, the instructions comprising:
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instructions for determining a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals including a current time interval; instructions for averaging the LPC coefficients over a plurality of successive time intervals preceding the current time interval; instructions for determining a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients; instructions for declaring the signal to be stationary in the current time interval when the cross-correlation exceeds a threshold value; and instructions for declaring the signal to be non-stationary in the current time interval when the cross-correlation is less than the threshold value. - View Dependent Claims (12, 13, 14, 15)
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16. A method of detecting transitions between an absence-of-speech state and a presence-of-speech state in an audio signal, the method comprising, in the absence-of-speech state detecting a transition to the presence-of-speech state by:
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determining a set of Linear Predictive Coding (LPC) coefficients characterizing spectral properties of the signal for each of a plurality of successive time intervals including a current time interval; averaging the LPC coefficients over a plurality of successive time intervals preceding the current time interval; determining a cross-correlation of the LPC coefficients for the current time interval with the averaged LPC coefficients; and declaring a transition to the presence-of-speech state when the cross-correlation is less than a threshold value. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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Specification