| 摘要 |
PURPOSE:To prevent confined sound from being generated due to resonance, by applying a vibration exciting force having a phase reverse to that of vibration transmitted from an engine or the like to an automobile windshield pane to cancel out the vibration of the windshield pane in a vector-like manner so that the vibration of the same is restrained. CONSTITUTION:A microphone 1 is arranged inside of the roof section of an automobile 2 to detect the sound pressure level of noise in the passenger's compartment. Further, a signal indicating noise in the passenger's compartment is amplified by an amplifier circuit 4 to a predetermined level, and is delivered to a phase compensating circuit 5 to obtain a signal having a reverse phase which is then applied to a piezo element 10 provided to, for example, the rear windshield pane 7 so that a vibration exciting force in the direction reverse to that of vibration transmitted from an engine or the like through solid mediums, is applied to the rear windshield pane 7. Thereby, it is possible to eliminate the vibration of the rear windshield 7 and therefore, it is possible to prevent confined sound from being generated due to resonance.
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