| 摘要 |
<p>A noise attenuator (20) which can reduce time and cost for installation thereof as compared with the conventional configuration and a vehicle air intake duct provided with the noise attenuator (20) are provided. The noise attenuator (20) includes a pair of circular through holes (13) formed through a duct wall (10W), a pair of wave transmitting/receiving membranes (21A, 21B) which are stretched so as to close the circular through holes (13), and a seesaw member (22) which connects between central portions of the paired transmitting/receiving membranes (21A, 21B). Accordingly, when one of the membranes (21A, 21B) receives a sound wave of noise thereby to be vibrated at a predetermined frequency, the other membrane (21A, 21B) follows it and is also vibrated while shifted by a half cycle. As a result, a cancellation wave with a phase opposite to the sound wave received by the one membrane (21A, 21B) is transmitted from the other membrane (21A, 21B), whereupon the noise can be attenuated. Moreover, since no electrical circuit for generating the cancellation wave is provided, the conventional dustproof or waterproof treatment and wiring processing are rendered unnecessary. This can realize low-cost installation of the noise attenuator (20).</p> |
