| 摘要 |
PURPOSE:To eliminate noise components by providing a first microphone unit which is disposed at about the same height as that of a noise source and a second microphone unit located higher than the former and obtaining the difference signal from between signals from the both microphones. CONSTITUTION:The microphone unit M1 is displised on a conference table 1, and the microphone unit M2 is placed above the former M1 at a prescribed distance. Both microphone units M1, M2 are nondirectional microphones, whose outputs are respectively supplied to amplifiers 11,12. The output from the unit M1 is delayed by a phase shifter 13, and attenuated by a gain control circuit 14. The output from the unit thus delayed by a prescribed amount and attenuated together with an output from the unit M2 are subtracted from each other in a subtraction circuit 15. With such a constitution as the above, the directivity shown in the figure can be obtained. As a result, noises from the noise sources in the vicinity of the surface of the conference table 1 can be eliminated. |
