Method and apparatus for reducing repetitive noise entering the ear

• US 4,654,871 A
• Filed: 04/03/1985
• Issued: 03/31/1987
• Est. Priority Date: 06/12/1981
• Status: Expired due to Fees

• Current Assignee: Chaplin Patets Holding Co., Inc.
• Original Assignee: Sound Attenuators Limited
• Inventors: Smith, Roderick A., Bramer, Terrence P. C., Chaplin, George B. B.
• Primary Examiner(s): Dwyer, James L.
• Application Number:
  US06/719,034
• Time in Patent Office: 727 Days
• Field of Search: 381/72, 381/74, 381/94, 181/206, 181/129
• US Class Current: 381/72
• CPC Class Codes: A61F 11/145 electric, e.g. for active noise reduction
• CPC Class Codes: G10K 11/178 by electro-acoustically regenerating the original acoustic waves in anti-phase
• CPC Class Codes: G10K 11/17823 Reference signals, e.g. ambient acoustic environment
• CPC Class Codes: G10K 11/17837 by retaining part of the ambient acoustic environment, e.g. speech or alarm signals that the user needs to hear
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17883 the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/121 Rotating machines, e.g. engines, turbines, motors; Periodic or quasi-periodic signals in general
• CPC Class Codes: G10K 2210/3011 Single acoustic input
• CPC Class Codes: G10K 2210/3032 Harmonics or sub-harmonics
• CPC Class Codes: G10K 2210/509 Hybrid, i.e. combining different technologies, e.g. passive and active

Abstract

Apparatus for improving the audibility of incident sound (4) to a person (3) operating in an environment where there is a substantial background noise field (2) coming from a source (1) of repetitive noise, comprises an adaptable waveform generator (7), a first electro-acoustic transducer (10) receiving a synthesized cancelling waveform from the generator (7) and generating a cancelling noise to at least partly null the background noise, a second electro-acoustic transducer (11) to sense the partially nulled background noise, and adaptor (13) to modify the output of the generator (7) on the basis of the electrical output signal from the second transducer to minimize the nulled background noise, and sensor (5) to feed a triggering signal (6) derived from the source to the waveform generator. The electro-acoustic transducers (10, 11) can be mounted in headset (8) holding the transducers adjacent to an ear of said person without substantially impeding the arrival of said incident sound (4) to said ear.

Claims

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.

2. Apparatus as claimed in claim 1, in which the apparatus is portable and the triggering signal is fed from the source to the apparatus by one of an optical link, an ultra-sonic link and an electrical link.

3. Apparatus as claimed in claim 2, in which there is a separate waveform generator for each first and second transducer.

4. Apparatus as claimed in claim 3, in which the triggering signal is fed to each waveform generator.

5. 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.

6. A method as claimed in claim 5, in which the apparatus is portable and the triggering signal is fed from the source to the apparatus by one of an optical link, an ultra-sonic link and an electrical link.

7. A method as claimed in claim 6, in which a separate adaptable waveform is fed to each first transducer and is separately modified by the output from the respective second transducer.

8. A method as claimed in claim 7, in which the triggering signal is fed to each waveform generator.