Patent ID: 6711540
Filing Date: 2004-03-23
Classification: G10L,H04Q

Abstract:
A dual-tone multi-frequency (DTMF) detector for detecting at least one tone having a known frequency and duration in an input signal, the input signal being input over a period of time, the period of time being divided into frame portions including at least an initial frame portion and a last frame portion, the apparatus comprising:means for generating an energy signal indicative of the energy of the input signal during each frame portion; a signal filter receiving the energy signal and generating a noise indicator based on the energy signal; a dynamic threshold determiner generating an energy threshold for each frame portion based on a value of the energy signal during a previous frame portion; and a signal processor receiving the energy threshold, the noise indicator, and the energy signal, and determining when the input signal includes the at least one tone based on the energy threshold, the noise indicator, and the energy signal.