Abstract: A method and apparatus for encoding/decoding of background sounds. The background sounds are encoded/decoded in a digital frame based speech encoder/decoder. First, it is determined whether the signal that is directed to the encoder/decoder represents primarily speech or background sounds. When the signal directed to the encoder/decoder represents primarily background sounds, the temporal variation between consecutive frames and/or the domain of at least one filter defining parameter is restricted.

Abstract: A receiver in a frame based radio communication system includes a speech decoder of the source-filter type which is controlled by internal state variable updated on a frame by frame basis for modifying received filter parameters representing background sounds transmitted over a communication channel. The receiver detects frames containing transmission errors, decides whether a frame in which transmission errors have been detected is acceptable, and conceals the detected transmission errors by restricting updating of at least one of the internal state variables if the detected frame is declared non-acceptable.

Abstract: A receiver in a frame based radio communication system includes a speech decoder of the source-filter type which is controlled by internal state variables updated on a frame by frame basis for modifying received filter defining parameters representing background sounds transmitted over a communication channel. The receiver detects frame loss and conceals the effects of frame loss by restricting updating of at least one of the internal state variables.

Abstract: A method and apparatus for improving the decoding of audio signals is disclosed. In a receiver of a frame based radio communication system, rejected frames are concealed according to a first algorithm if the last accepted frame was a speech frame and according to a second algorithm if the last accepted frame was a frame containing background sounds.