| 摘要 |
PCT No. PCT/GB80/00128 Sec. 371 Date Apr. 16, 1981 Sec. 102(e) Date Apr. 14, 1981 PCT Filed Aug. 15, 1980 PCT Pub. No. WO81/00638 PCT Pub. Date Mar. 5, 1981.A method of reducing the adaption time needed to adapt a synthetically generated secondary waveform so that it nulls a primary repetitive waveform (e.g. noise) from a source (1) of vibration, the secondary waveform generation (5) being synchronized by the source (1). The clarity and/or the amplitude of at least a part of the signal resulting from interaction between the primary and secondary waveforms is sensed (6) and used (7, 8) to reshape the secondary waveform. The invention finds application in the cancelling of repetitive vibrations (e.g. in quietening the driving cab of a vehicle).
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