| 摘要 |
PURPOSE:To enable highly accurate pitch extraction with a simple construction, by calculating an extreme value point by a curve interpolation using more than one digital data containing an extreme value. CONSTITUTION:An acoustic signal with a limited band by HPF 1 and LPF 2 is converted into a digital data with an A/D converter 3 to detect a maximal value or a minimal value of the digital data with an extreme value detecting section 9. The number of samples in the digital data which is inputted into a control section 8 synchronizing a clock indication signal outputted from the detecting section 9 is counted with the control section 8 to determine an almost period of a pitch. At the same time, at least more than one digital data containing an extreme value at both ends of the almost period are read out of a memory 7 to calculate an extreme value point by a curve interpolation using the digital data read out at the control section 8. Then, the results of the calculation are added to the almost period to output a pitch period. This enables the obtaining of a pitch without causing variations in extraction accuracy with a sampling frequency. |
