초록 ▼

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

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).

대표청구항 ▼

A method of reducing the amplitude of primary vibration pulses received at a selected location from a source of recurring primary vibration, which method comprises feeding specially synthesised pulses of secondary vibration to said location, the generation of the said pulses of secondary vibration b

A method of reducing the amplitude of primary vibration pulses received at a selected location from a source of recurring primary vibration, which method comprises feeding specially synthesised pulses of secondary vibration to said location, the generation of the said pulses of secondary vibration being triggered by a signal derived from the source, and the waveform of the said synthesised pulses of secondary vibration being adapted with respect to the time to improve the extent to which the secondary vibration nulls the primary vibration at the said location, characterised in that the time taken to evolve a successful adaption of the pulses of secondary vibration is reduced by monitoring the pulses of residual vibration at the said location which result from interaction between each primary vibration pulse and the respective pulse of secondary vibration, and effecting the adaption of the waveform of the pulses of secondary vibration on the basis of the amplitude and/or the polarity of a pulse of the residual vibration cyclically sensed in a plurality of successive time intervals, each separate sensing being used in the derived sequence to control the adaption of a different part of the waveform of a subsequent pulse of the secondary vibration.