| 摘要 |
PURPOSE: To enable picking up of an effective sound from an object by arranging a double sensor between a noise source and the object. CONSTITUTION: A microphone M1 directed at a noise source S is linked to a control circuit R and then, an anti-noise source A is controlled. The anti-noise source A is arranged between the noise source S and a double sensor and the double sensor is positioned in a radiation range of the anti-noise source. The microphone M1 belonging to an anti-noise system picks up a noise PS unweakened whereas an effective sound P from an object is weakened according to a front/rear ratio of the microphone as a result of directional characteristic. A microphone M2 set away from the noise source S being directed at an object to be measured properly senses and picks up the effective sound P unweakened from the object and the weakened undesired noise PS in terms of directivity. |
