| 摘要 |
PURPOSE:To make a receiver on the side of a speech decoding device hardly feel unnatural by forcibly updating a background noise when a background noise deciding circuit detects variation in characteristics of an input speech signal in a voiceless state. CONSTITUTION:The background noise update decision circuit 20 detects whether or not the input speech signal varies in characteristics in the voiceless state according to a synthesis filter coefficient and a frame energy value and outputs the result to a control circuit 17. If a voiced/voiceless sound decision circuit 14 detects the voiceless state when a speech encoding circuit 15 is in operation, the control circuit 17 encodes the current frame as a background noise frame and then stops the operation of the speech encoding circuit 15 temporarily, and, in the case where a voiced state is detected when the speech encoding circuit 15 is in the stop state, the operation of the speech encoding circuit 16 is restarted. Thus, when the background noise update decision circuit 20 detects the input speech signal varying in characteristics, the background noise is forcibly updated. |
