Method and apparatus for reducing repetitive noise entering the ear

Claim 1

Apparatus for improving the audibility of desired incident sound to a person operating in an environment where there is a substantial background noise in the person's ears coming from a source of repetitive noise, comprising an adaptable waveform generator, head-mounted means including two ear pieces one for each ear of the wearer, each ear piece being equipped with a first electro-acoustic transducer receiving a synthesised cancelling waveform from the generator and generating a cancelling noise adjacent to the respective ear of the person to at least partly null the background noise in that ear, a second electro-acoustic transducer to sense the partially nulled background noise in the person's ear, adaptive means to modify the output of the generator on the basis of the electrical output signal from one of the second transducers to minimize the nulled background noise, the head-mounted means holding the transducers adjacent to the respective ear of the person while allowing said desired incident sound to reach each ear, and means to feed a triggering signal derived from the source to the waveform generator, the apparatus further comprising a third electro-acoustic transducer for picking up the repetitive noise from said source and speech signals from the said person and generating a further electrical output which is characteristic of the noise and speech signals, the further electrical output from said third electro-acoustic transducer being electrically combined with the electrical output from said waveform generator in an opearting means to selectively reduce the effect of the repetitive noise coming from said source on the further electrical output of the third electro-acoustic transducer without significantly affecting the component of said further electrical output which is generated by said speech signals.

Claim 6

A method for improving the audibility of desired incident sound to a person operating in an environment where there is a substantial background noise in the person's ears coming from a source of repetitive noise, which method comprises generating an adaptable electrical waveform, feeding the waveform to a respective first electro-acoustic transducer mounted adjacent to each ear of the person to generate a cancelling noise adjacent to the respective ear of the person to at least partly null the background noise in that ear, sensing the partially nulled background noise in each ear with a respective second electro-acoustic transducer, modifying the output of the generator on the basis of the electrical output signal from one of the second transducers to minimize the nulled background noise and allowing said desired incident sound to reach each ear, feeding a triggering signal derived from the source to the waveform generator, the method further comprising using a third electro-acoustic transducer to pick up the repetitive noise from said source and speech signals for the said person and generate a further electrical output which is characteristic of the noise and speech signals, the further electrical output from said third electro-acoustic transducer being electrically combined with the electrical output from said waveform generator to selectively reduce the effect of the repetitive noise coming from said source on the further electrical output of the third electro-acoustic transducer without significantly affecting the component of said further electrical output which is generated by said speech signals.

Claim 7

A method for improving the audibility of desired incident sound to a person operating in an environment where there is a substantial background noise in the person's ears coming from a source of repetitive noise, which method comprises generating an adaptable electrical waveform, feeding the waveform to a respective first electro-acoustic transducer mounted adjacent to each ear of the person to generate a cancelling noise adjacent to the respective ear of the person to at least partly null the background noise in that ear, sensing the partially nulled background noise in each ear with a respective second electro-acoustic transducer, modifying the output of the generator on the basis of the electrical output signal from one of the second transducers to minimize the nulled background noise and allowing said desired incident sound to reach each ear, feeding a triggering signal derived from the source to the waveform generator, the method further comprising using a third electro-acoustic transducer to pick up the repetitive noise from said source and speech signals for the said person and generate a further electrical output which is characteristic of the noise and speech signals, the further electrical output from said third electro-acoustic transducer being electrically combined with the electrical output from said waveform generator to selectively reduce the effect of the repetitive noise coming from said source on the further electrical output of the third electro-acoustic transducer without significantly affecting the component of said further electrical output which is generated by said speech signals.