| 摘要 |
PURPOSE:To reduce the fatigue of an ear at the time of photographing for a long period by impressing the output of a microphone through a low pass filter, which attenuates frequencies at >= a value obtained with dividing the propagating speed of a voice by the shortest spatial distance between the microphone and a speaker. CONSTITUTION:Instead of a phase variable circuit in a usual constitution, a low pass filter 5, which attenuates the frequencies at >= the minimum resonant frequencies f0 calculated by the shortest spatial distance l between a microphone 1 and a speaker 4, is inserted. Consequently, since a resonant phenomenon is generated in the zero condition of a speaker output and a microphone input, a hawling phenomenon is generated by the amplification of the minimum resonant frequencies f0, and the voice input level to the speaker 4 can be reduced by the low pass filter 5, which attenuates the frequencies at >= the minimum resonant frequencies. Thus, the generation of the hawling is prevented, and the fatigue of the ear at the time of photographing for a long period can be reduced. |
