| 摘要 |
PURPOSE:To perform pitch extraction to only sound sections by first comparing inputted acoustic signals with a background noise level by means of a noise level deciding means so as to obtain signals indicating presence/absence of sounds. CONSTITUTION:Inputted acoustic signals are first digitized by means of an A/D converter 1 and inputted to a noise level deciding section 2 where the signals are held by a hold circuit 21 and used as a background noise level. Then the inputted acoustic signals are compared with the background noise level and whether or not no sound exists is outputted to a gate 3. When the level of the inputted acoustic signals is lower than 1.4 times of the background noise level, it is decided that no sound exists. When no sound exists, the gate 3 is turned off and no digital acoustic signal output is inputted to a multiplier circuit 5. As a result, a pitch extractor which outputs nothing when no sound exists and performs pitch extraction only when sounds exist can be obtained. |
