Abstract: A system for creating a comfort noise signal, said system includes a clipping circuit, a comfort noise generator, and a switch. The clipping circuit receives a near-end signal, a far-end signal and a residual signal. The clipping circuit determines the power of the far-end signal, the power of the near-end signal and the power of the residual signal. The clipping circuit determines the ratio of the power of the near-end signal to the residual signal and whether the ratio is less than a predetermined threshold. A comfort noise determination block is coupled to the residual signal and selectively forms a comfort noise signal. A switch is coupled to the comfort noise determination block and the clipping circuit. The switch is activated to transmit the comfort noise signal whenever the ratio of the power of the near-end signal to the residual signal is less than a predetermined threshold.

Abstract: An audio processing module, in accordance with the invention, includes an input for receiving input signals. A side tone generator is included for receiving the input signals and for generating a side tone to be output. A noise suppressor is coupled to the input for suppressing noise of the input signal prior to a coding process, the noise suppressor providing feedback to the side tone generator to adjust a gain of the input signal to the output. A method for adjusting the gain of the side tone generator is also included.

Abstract: A system and method for DTMF tone detection receives an input signal. The input signal includes a DTMF tone. The DTMF tone has a first frequency and a second frequency. An initial first frequency and an initial second frequency of said DTMF tone are selected by calculating a plurality of cost functions. The initial first frequency is confirmed to be the first frequency and the initial second frequency is confirmed to be the second frequency using re-computed values of the plurality of cost functions.

Abstract: Methods and systems for echo cancellation are provided. According to one method, when a far end signal with an echo having a major body and a pure delay portion is received, a filter having a finite length is provided. Once the finite length filter covers a portion of an echo path, the method includes determining whether at least a portion of the echo major body is within the filter. In one embodiment, the filter is divided into a plurality of sub-windows, and the step of determining whether the filter covers the major body of the echo path includes using filter coefficients of the first sub-window. According to one embodiment, the major body of the echo path is detected by comparing a maximum value coefficient in the first sub-window with a predetermined threshold value. If the maximum value coefficient is greater than the threshold value, the major body is detected.

Abstract: In a full duplex audio telecommunication system, it is desirable to determine whether a transmitted signal contains a signal component generated exclusively at one end of the communication path. A removal filter is connected to receive a Far-End signal and to remove a signal component therefrom. A detection filter is connected to receive a Near-End signal and to detect the presence of a signal component corresponding to the component removed from the Far-End signal. A decision stage connected with the detection filter responds to the detection filter by actuating a control signal when signal activity in the selected signal component is detected. The control signal is used to control adaption of an AFIR filter of an echo canceler to prevent adaption during intervals of Near-End speech activity. The selected signal component preferably comprises a predetermined frequency range.