Kabushiki Kaisha Toshiba

Takuro Hayashi

Akihiko Enamito

Shinichi Noda

Tsutomu Shioyama

Nobutake Aikura

Kunio Matsukura

Satoshi Aoyagi

A three-dimension active silencer includes a measuring unit for detecting a signal relating to a sound radiated from a target sound source which is located in a closed box. A plurality of additional sound sources are arranged around the target sound source. A microphone is arranged at a predetermined position for detecting a sound power at the position. A controller is adapted to control respective amplitudes of the additional sound sources which can be different from an amplitude of the target sound source and respective phases of the additional sound sources, based on the signal detected by the measuring unit, in such a manner that the microphone detects the lowest sound power. The additional sound sources are arranged in such a manner that a position xof the target sound source, respective relative positions d(i=1, 2, . . . , N) of the N additional sound sources from the target sound source and a wave number k of the sound radiated from the target sound source can substantially satisfy the following expression.According to the feature, it can be achieved to reduce the total sound power in the closed box including the target sound source.

Three-dimension active silencer

A speaker, serving as an additional sound source, is provided close to a noise source, two microphones are arranged on a central axis of a vibration surface of the speaker to be spaced from each other, acoustic intensity of the speaker is measured from outputs of these microphones, and an input to the speaker is controlled by a controller such that acoustic intensity, that is, acoustic power of the speaker is set to be zero or minimized.

Active noise control apparatus

An impeller used for cooling a dynamoelectric machine such as electric motors includes a disk and a plurality of blades arranged on the disk in a circle at unequal spaces so that a position angle .theta.n of an n-th blade is met by an equation:

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Yokohama, Japan

Takuro Hayashi