A signal processor such as an ADPCM decoder (128b) receives an input signal. As part of the CCITT Recommendation G.726 algorithm, an inverse adaptive quantizer (41) processes the input signal to provide a quantized difference signal dq(k). When enabled, a noise detector (50) samples signal dq(k) once for each of a predetermined number of received samples. The noise detector (50) adds the absolute value of signal dq(k) to a total energy estimate. At the end of the predetermined number of samples, the noise detector (50) compares the total energy estimate to a product of a noise threshold and the predetermined number. If the total energy estimate exceeds this product, then a noise indication is provided. In another embodiment (228b) a noise detector (250) compares an existing energy estimate signal dml(k) computed by an adaptation speed control block (48) as part of the G.726 algorithm to an energy threshold to save processing time. <IMAGE>
Noise burst detection in an ADPCM decoder.