| 摘要 |
PURPOSE:To obtain a parametric speaker excellent in safety and sharp in direction b using an acoustic filter attenuating a first wave effectively and scarcely giving an influence to a sound pressure and the direction of a second wave. CONSTITUTION:A sound source comprises an array type transducer. The acoustic filter 24 constituted by a polyethylene film 22 of thickness of 18mum and a spacer 23 of thickness of 1cm. The distance between the sound source 21 and the filter 24 is 1.5m and he distace between the filter 24 and a microphone 25 is 1m. According to such construction, a sharp direction peculiar to the speaker is not broke and the influence to the human body due to a strong ultrasonic wave can be eliminated. Further, b replacing the filter 24 by a filter 27 formed b inserting a spacer 20 cutting soft polyurethane foam into grid between the films 22, films 22 can be avoided to be bonded to each other and without deteriorating a filtering feature, setting direction can be optionally selected. |
