| 摘要 |
PROBLEM TO BE SOLVED: To improve counting precision while counting a period of a sound signal with a count value of a sampling clock by repeatedly executing period measurement in a prescribed period and finding weighted mean of plural obtained count values. SOLUTION: In a period detecting part 40, a noise property decision part 60 decides a singing sound signal having repeated irregular zero cross of too short period as a noise signal. An LPF 61 removes the noise signal and a harmonic component to supply the fundamental frequency of the singing sound signal to a count operation part 62. The count operation part 62 counts the zero cross interval of the inputted singing sound signal at the period of the sampling clock, and weighted mean of plural zero cross intervals is found. The number of average zero cross intervals is not fixed, and all timewise intervals of the zero cross occurring for a fixed time just before counting are averaged. When the frequency (period) of the sound signal is detected, as the period of the weighted mean, about 20ms is suitable. |
