| 摘要 |
PURPOSE:To reduce pitch detection errors by making the detection range of a pitch narrow in case of a large average amplitude width and making the detection range of the pitch period wide in case of a small average amplitude width. CONSTITUTION:Sound waveform data is inputted to average amplitude width calculating circuit 203 and auto-correlation value calculating circuit 204 through input terminal 201. Maximum value detector circuit 206 detects the maximum value from circuit 204 according to data from retrieval range data generator circuit 205, and not only outputs data from output terminal 212 but also feeds back data to circuit 205. Circuit 205 leads out retrieval width data from retrieval range data table 207 according to average amplitude width data from circuit 203 and generates the value, which is obtained by adding the retrieval width data above to data fed back from circuit 206, as the upper limit value of the detection range in the next frame and outputs this value as control data of circuit 206. Pitch period data are outputted successively by repeating this operation. |
