Fujitsu Ten Limited

Masahiro Babasaki

Kazuya Sako

Kazuhiro Sakiyama

Masaaki Nagami

A noise control device disposed at the outlet of a tail pipe which emits exhaust noise of an automobile to silence noise from the tail pipe comprises a speaker which is arranged near the tail pipe and of which the open surface has a constant angle with respect to a vertical plane, an enclosure which closes the rear portion of the speaker, and a silencing sound guide portion which guides silencing sounds emitted from the front surface of the speaker to the outlet of the tail pipe. A closed space into which a bumper for absorbing impact in case of collision is made, is used as a resonant-cavity of said speaker. Based on the amount of silencing noise which becomes greater as a plurality of microphones are arranged to be closer to the speaker, the outputs of the plurality of microphones apart a constant distance from said speaker are synthesized.

Noise control device

In a noise controller which forms a noise cancelling sound having a phase opposite to and a sound pressure equal to those of a noise infiltrating into a closed space, any deviation in its transfer characteristics from the initial equalization is easily checked and judged owing to the provision of an adaptive filter which automatically varies the filter coefficient and forms a cancelling signal for forming a cancelling sound, a coefficient updating means which updates the filter coefficient based on an error signal after the noise has been cancelled, a simulated transfer characteristics compensation means which forms the initial equalization by simulating transfer characteristics of a transmission path via the space in which the noise is to be cancelled and forms a reproduced reference signal, a white noise generating means which generates white noise to check the initial equalization, and an initial equalization judging means which judges the accuracy of the initial equalization based on a ratio (S/N) of the reproduced reference signal obtained from white noise to the error signal. A change in the conditions for cancelling noise is detected in the closed space, and any deviation from the initial equalization is judged.

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Takatsuki, Japan

Masahiro Babasaki