Abstract: An apparatus for pre-processing a speech signal capable of improving the performance of speech signal processing by extracting the characteristics of noise that are distinguished from those of speech, and a method for extracting a speech end-point for the apparatus are provided. The apparatus includes a noise/speech determination unit for calculating noise information from at least one of an initial frame and a final frame of an input speech signal and determining if a current frame of the speech signal is a noise frame or a speech frame using the noise information, a hangover application unit for determining a predetermined number of frames transmitted after the current frame as consecutive speech frames when the current frame is the speech frame, and a speech information update unit for storing the speech frame and the consecutive speech frames.

Abstract: An apparatus for canceling an echo signal in a mobile terminal of a mobile communication system. A double talk detector (DTD) receives a first signal by canceling an estimated echo signal from a signal received through a microphone, outputs the first signal, and outputs the first and a second signal comprising a background noise signal and a residual echo signal during a non-double talk. An Auto-Regressive (AR) analysis and inverse filtering unit receives the second signal from the DTD, and whitens the second signal. A pitch analysis and inverse filtering unit receives the whitened signal, and cancels a pitch value remaining therein by performing pitch analysis and inverse filtering on the whitened signal. A noise canceller receives the pitch-cancelled whitened signal and the first signal output from the DTD, canceling a residual echo signal and a background noise signal from the first signal using the pitch-cancelled whitened signal.

Abstract: An automatic gain controller and a method using the same are provided. The automatic gain controller and method analyze background noise by operating a microphone mounted in a mobile communication terminal and automatically control the gain of the signal part which is non-audible due to the background noise. Thus, a user may listen to music by using an earphone or a headphone connected to the mobile communication terminal in an environment with background noise. The method includes receiving an audio signal to be reproduced, receiving a background noise signal introduced through a microphone, controlling a gain of the audio signal by comparing the background noise signal and the audio signal and outputting the gain-controlled audio signal so that the user can listen to the gain-controlled audio signal.

Abstract: An acoustic echo canceller (AEC) apparatus for canceling an echo signal input to a microphone in a mobile terminal. In the AEC apparatus, a first analysis filter bank divides a signal received from the microphone into a plurality of subband signals, and classifies the subband signals into high-band signals and low-band signals according to a predetermined reference. A second analysis filter bank divides a far-end user's signal into a plurality of subband signals, and outputs particular subband signals being lower than or equal to a reference band to an adaptive filter bank. The adaptive filter bank receives the subband signals output from the second analysis filter bank, and generates estimated echo signals for the individual subbands. An adder calculates differences between the low-band signals among the subband signals output from the first analysis filter bank and the estimated echo signals output from the adaptive filter bank.

Abstract: A method and apparatus for canceling an acoustic echo in a mobile terminal involving an acoustic echo canceller (AEC) for canceling an echo signal from a received far-end user's signal. Upon detecting double talk, a down-sampler lowpass-filters an output signal and down-samples the lowpass-filtered signal. The AEC estimates an echo signal using the far-end user's signal, and outputs a residual echo signal by canceling the estimated echo signal from the down-sampled signal. An up-sampler up-samples the residual echo signal by zero padding, and lowpass-filters the up-sampled signal.

Abstract: An apparatus and method for canceling an acoustic echo. In the apparatus, a double-talk detector detects whether a current period is a double-talk period or a single-talk period by determining whether a remote talker's signal and a local talker's signal are received simultaneously or at different times. A noise-robust affine projection (NRAP) adaptive filter estimates an acoustic echo included in the remote talker's signal using an NRAP algorithm if the detected current period is a double-talk period. A normalized least mean square (NLMS) adaptive filter estimates the acoustic echo included in the remote talker's signal using an NLMS algorithm if the detected current period is a single-talk period. The apparatus then generates an echo-canceled local talker's signal.

Abstract: An apparatus for canceling an echo signal in a mobile terminal of a mobile communication system. A double talk detector (DTD) receives a first signal by canceling an estimated echo signal from a signal received through a microphone, outputs the first signal, and outputs the first and a second signal comprising a background noise signal and a residual echo signal during a non-double talk. An Auto-Regressive (AR) analysis and inverse filtering unit receives the second signal from the DTD, and whitens the second signal. A pitch analysis and inverse filtering unit receives the whitened signal, and cancels a pitch value remaining therein by performing pitch analysis and inverse filtering on the whitened signal. A noise canceller receives the pitch-cancelled whitened signal and the first signal output from the DTD, canceling a residual echo signal and a background noise signal from the first signal using the pitch-cancelled whitened signal.