| 摘要 |
PURPOSE:To make the directivity of a microphone suitable for room circumstance and eliminate the need for speaking directly toward the microphone by varying the directivity of the microphone depending upon the extent of attenuation time of the reverberation in the room. CONSTITUTION:When a switch 26 is turned off for a specified time, short waveforms superposed by outputs of both the short waveforms oscillator 27 and white-noise oscillator 28 are delivered in the room from a speaker. The short waveform signals are inputted in the microphone 1 together with the reverberation and rectified and smoothed voltages Vr attenuates with the lapse of time. In addition, an output of a comparator 32 turns a FF 36 on and the comparator 33 turns the FF 36 off. An AND circuit 37 opens during an on-time of FF 36 and switches 42-44 are closed by the outputs of counters 39-41, depending upon the on-time period of FF 36. Thus the microphone 1 having variable directivity delivers non-directivity in the room having a short reverbera tion time, while it delivers single directivity in the room having a long reverbera tion time and it delivers medium directivity in the room having a medium reverberation time. |
