| 摘要 |
<p>PURPOSE:To improve an SN ratio by preventing a loss of level at a low frequency and also by reducing the correction amount of an equalizer, by adding the output of a microphone to that of the other microphone via a variable high-pass filter reversely in phase. CONSTITUTION:The first order pressure gradient unidirectional microphones 2a and 2b are arranged on axis (l) while facing forth to sound source 1. The output of microphone 2a has a low frequency component attenuated by variable high- pass filter 6 capable of varying a cut-off frequency and is mixed by mixer 7 with the out-of-phase output of microphone 2b. When the cut-off frequency of filter 6 is low, outputs of microphones 2a and 2b are mixed by subtraction over a wide frequency range to obtain the second order unidirectivity and when the cut-off frequency is high, the output of microphone 2b is extracted being greater than that of 2a, so that the first order unidirectivity can be obtained.</p> |
