Abstract: Method and apparatus for detecting voice activity in an audio signal, the method comprising computing the autocorrelation coefficients of the signal, identifying a first autocorrelation vector whose components comprise a first series of autocorrelation coefficients, identifying a second autocorrelation vector whose components comprise a second series of autocorrelation coefficients offset from the first series by a predetermined offset value, subtracting the first autocorrelation vector from the second autocorrelation vector to obtain a differentiation vector, and computing a norm of the differentiation vector, which differentiation vector norm represents a first indicator of voice activity.