| 摘要 |
PURPOSE:To stably extract only a fundamental wave component, by using BPF of which the central frequency is controlled by clock frequence and fixing the central frequency of BPF in the vicinity of the fundamental frequency of a musical sound signal to measure the frequency of output. CONSTITUTION:An inputted music signal 301 is received by a receiving part 31 and supplied to BPF34 and a level sensor 33 through an amplifier circuit 32. A clock frequency control circuit 35 receives the output of the sensor 33 to scan the central frequency of BPF34 form low frequency. When a peak detection circuit 38 detects a peak, the circuit 35 fixes a clock signal 305. The output of BPF34 is sent to a frequency count circuit 41 through a wave form shaping circuit 37 and a gate 40. The count value is converted by a decoder circuit 42 and displayed as the height of musical sound or the shift from a reference value by a display appratus 43. When new music sound is inputted, similar operation is performed and only a fundamental wave component can be extracted regardless of the height of music sound. |
