| 摘要 |
PURPOSE:To erase a display based upon an acoustic wave from a coexisting sound source from a display screen immediately through simple operation by specifying the generation direction of a null point (direction acoustic wave arrival from a noise source) when the acoustic wave arriving from the unnecessary noise source exerts influence, and outputting a pseudo pattern signal. CONSTITUTION:A receiver 1 has two orthogonal 8-shaped bipolar directivity patterns and a nondirectivity pattern and outputs a received signal when an acoustic wave arrives, and a pattern generator 7 outputs the pseudo pattern signal equivalent corresponding to a signal received with a directivity pattern having a null point in the specified direction. Then when the display screen of a display device 6 becomes hard to see in the arrival direction of the acoustic wave owing to the influence of the unnecessary noise source, a null direction specifying circuit 9 specifies the direction of null point generation to the generator 7, so that the pseudo pattern signal having a null point in the specified direction is outputted. Further, the pseudo pattern signal is applied to phase comparators 3a and 3b through a switching circuit 8, so only the direction of the arrival of the acoustic wave from the sounding source is displayed clearly. |
