| 摘要 |
<p>PURPOSE:To suppress a sound pressure in the vicinity of a microphone without causing oscillation by using a band pass filter having a prescribed characteristic. CONSTITUTION:A sound pressure controller consists of a microphone 1, a microphone amplifier 2, a band pass filter 3, an amplifier 4 and a speaker 5. The phase characteristic of the filter 3 is 0 deg. at a specific frequency characteristic and within a range from 90 deg. to -90 deg. with respect to other frequency components. For example, the filter 3 consists of filters F1, F2 and F3 so as to adjust the frequency characteristic f1 independently. It is possible to suppress the sound pressure over a wide band more than that of a single band pass filter by adjusting the characteristics of the filters F1, F2 and F3. Thus, the sound pressure in the vicinity of the microphone is suppressed without causing any oscillation.</p> |
