| 摘要 |
PURPOSE:To prevent noise from spreading to the neighborhood and to improve acoustic effect to an objective person by providing an acoustooptic transducer which reproduces an original audible tone by the nonlinearity of air on a railroad crossing or pedestrian crossing, and radiating the acoustic wave from the electroacoustic transducer to passersby. CONSTITUTION:Nonlinear parametric speakers 101-106 which have very narrow directivity are used as alarms of a railroad crossing and installed over a road 11. In this case, plural speakers may be fitted in parallel so as to generate an acoustic wave in the same direction and widen the service area. In general, an alarm installed on a railroad crossing is for giving a warning to persons and bicyclists walking or riding on the road ahead, and the conventional alarm has wide directivity, so an acoustic wave is radiated in every direction, causing a noise pollution to a neighboring residential area, specially, at night. On the other hand, when those nonlinear parametric speakers are used instead of the alarm, only persons and car drivers walking and driving on the road ahead are given a warming and no noise disturbs the neighborhood. |
