Method and apparatus for performing noise cancelling and headphoning

• US 5,134,659 A
• Filed: 07/27/1990
• Issued: 07/28/1992
• Est. Priority Date: 07/10/1990
• Status: Expired due to Fees

• Current Assignee: MNC, Inc.
• Original Assignee: MNC, Inc.
• Inventors: Moseley, William T.
• Primary Examiner(s): Isen, Forester W.
• Application Number:
  US07/558,342
• Time in Patent Office: 732 Days
• Field of Search: 381/72, 381/71, 381/163, 381/169
• US Class Current: 381/72
• CPC Class Codes: A61F 11/145 electric, e.g. for active noise reduction
• CPC Class Codes: B60G 2400/61 Load distribution
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: G10K 11/17825 Error signals
• CPC Class Codes: G10K 11/1783 handling or detecting of non-standard events or conditions, e.g. changing operating modes under specific operating conditions
• CPC Class Codes: G10K 11/17853 of the filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17861 using additional means for damping sound, e.g. using sound absorbing panels
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 11/17885 additionally using a desired external signal, e.g. pass-through audio such as music or speech
• CPC Class Codes: G10K 2210/108 Communication systems, e.g. where useful sound is kept and noise is cancelled
• CPC Class Codes: G10K 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/3013 Analogue, i.e. using analogue computers or circuits
• CPC Class Codes: G10K 2210/3019 Cross-terms between multiple in's and out's
• CPC Class Codes: G10K 2210/3045 Multiple acoustic inputs, single acoustic output
• CPC Class Codes: G10K 2210/3214 Architectures, e.g. special constructional features or arrangements of features
• CPC Class Codes: H04R 1/1008 Earpieces of the supra-aural or circum-aural type
• CPC Class Codes: H04R 1/1083 Reduction of ambient noise active noise reduction per se G10K11/175; protective devices for the ear, e.g. providing acoustic protection A61F11/06
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04R 5/033 Headphones for stereophonic communication details thereof, e.g. relating to batteries, cables or control elements H04R1/10

Abstract

A device for performing electroacoustic functions including noise cancellation, communication interface, and headphone functions. The device includes a composite transducer which is connected to a control unit. The composite transducer, which is adapted for use with the human ear, includes at least three transducers, oriented to be substantially coplanar to each other: two oppositely oriented input transducers for converting acoustic waves into electrical signals, and at least one output transducer oriented facing the ear for converting electrical signals into acoustic waves. The control unit includes circuitry for driving the output transducer based on electrical signals from the input transducers with an amplitude and phase to perform the noise cancellation, sound filtering, communication interface, and headphone functions. The input transducer which is oriented facing the ear picks up residual noise present in the ear canal which was not cancelled by the first input transducer to output transducer signal path due to non-ideal frequency and amplitude characteristics. The second input transducer supplies an electrical signal corresponding to the residual noise to the control circuitry to cancel the residual noise. Additionally, the path of acoustic energy from a noise source, through the composite transducer, and to the ear canal can be lengthened by the addition of a baffle around which the acoustic energy must travel.

Claims

1. An open air composite transducer assembly for use in cancelling sound waves in an ear canal, comprising:

a first input transducer for converting sound waves incident on a pickup surface of the first input transducer into corresponding input electrical signals, the pickup surface of the first input transducer facing in a first direction;

a second input transducer for converting sound waves incident on a pickup surface of the second input transducer into corresponding input electrical signals, the pickup surface of the second input transducer facing in a direction opposite said first direction;

an output transducer including a diaphragm for converting output electrical signals into corresponding sound waves which emanate from said diaphragm surface of the output transducer into said ear canal, the diaphragm surface facing in a direction opposite said first direction; and

a frame structure to which said first and second input transducers and said output transducer are fixed so that said pickup surfaces of said first and second input transducers and said diaphragm surface of said output transducer are in substantially the same plane.

2. The open air composite transducer assembly of claim 1, further comprising:

a baffle disposed substantially in a plane perpendicular to said first direction such that at least a portion of the baffle is located a distance in said first direction from said pickup surface of said first transducer, said baffle being made of a material through which acoustic energy does not readily pass.

3. The open air composite transducer assembly of claim 2, wherein said baffle is disc-shaped.

4. The open air composite transducer assembly of claim 1, further comprising:

a cushion means for cushioning the second input transducer, the output transducer, and the frame structure away from the ear, and for impeding the free flow of air parallel said same plane between the ear and the pickup surface of the second input transducer.

5. The open air composite transducer assembly of claim 4, wherein the cushion means is made of an open cell foam material which passes all frequencies of sound.

6. The open air composite transducer assembly of claim 1, further comprising:

an open cell cushion which substantially surrounds and encases the entire frame structure with the first and second input transducers and the output transducer fixed thereto.

7. The open air composite transducer assembly of claim 1 wherein the first and second transducers are fixed to the frame structure so that the frame structure, diaphragm of the output transducer, and first and second input transducers form an airtight barrier which lies substantially in said same plane.

8. An electroacoustic device for cancelling sound waves in a ear canal, comprising:

a first input transducer for converting sound waves incident on a pickup surface of the first input transducer into corresponding input electrical signals, the pickup surface of the first input transducer facing in a first direction;

a second input transducer for converting residual sound waves from said ear canal which are incident on a pickup surface of the second input transducer into corresponding input electrical signals, the pickup surface of the second input transducer facing in a direction opposite said first direction;

an output transducer including a diaphragm for converting output electrical signals into corresponding sound waves which emanate from said diaphragm surface of the output transducer into said ear canal, the diaphragm surface facing in a direction opposite said first direction; and

a frame structure to which said first and second input transducers and said output transducer are fixed so that said pickup surfaces of said first and second input transducers and said diaphragm surface of said output transducer are in substantially the same plane; and

a control means for receiving the electrical signals from the first input transducer and for generating a first component of the output electrical signals to the output transducer, the first component of the output electrical signals being substantially 180 degrees out of phase with respect to a frequency range of said sound waves incident on said pickup surface of said first input transducer, the control means also being for receiving the electrical signals from the second input transducer and for generating a second component of the output electrical signals to the output transducer, the second component of the output electrical signals being substantially 180 degrees out of phase with respect to said residual sound waves in the ear canal which are incident on said pickup surface of said second input transducer.

9. The electroacoustic device of claim 8, further comprising:

a cushion means for cushioning the second input transducer, the output transducer, and the frame structure away from the ear, and for impeding the free flow of air parallel to said same plane between the ear canal and the pickup surface of the second input transducer.

10. The electroacoustic device of claim 9, wherein the cushion means is made of an open cell foam material which passes all frequencies of sound.

11. The electroacoustic device of claim 8, wherein said residual sound waves in the ear canal are substantially limited to be outside said range of frequencies, and wherein the control means includes a filter for ensuring that the second component of the output electrical signals to the output transducer is substantially free of frequency components within said range of frequencies.

12. The electroacoustic device of claim 8, wherein the output transducer is a dynamic speaker, the control means including a low pass filter for filtering out middle and high frequency components from the second component of the output electrical signals to the output transducer.

13. The electroacoustic device of claim 8, wherein the control means disables the output transducer when the electrical input signals from the second input transducer exceed a predetermined amplitude.

14. A method for cancelling incoming noise entering an ear canal and for cancelling residual noise present in an ear canal, comprising the steps of:

detecting the incoming noise with a first input transducer and generating an electrical signal indicative of the incoming noise;

providing the electrical signal indicative of the incoming noise to an output transducer so that first acoustic waves are input into the ear canal that are phase shifted substantially 180 degrees with respect to the incoming noise, the first acoustic waves cancelling a component of said incoming noise which lies in a known frequency range within which said output transducer has a flat amplitude response;

detecting said residual noise with a second input transducer and generating an electrical signal indicative of the residual noise; and

providing the electrical signal indicative of the residual noise to said output transducer so that second acoustic waves are input into the ear canal that are phase shifted substantially 180 degrees with respect to the residual noise, the electrical signal indicative of the residual noise being filtered so that frequency components in said known frequency range are removed, the second acoustic waves cancelling a component of said incoming noise which lies outside said known frequency range.

15. The method of claim 14, wherein said first input transducer and said output transducer are disposed in substantially the same plane.

16. The method of claim 15, wherein said first input transducer is disposed facing in a first direction and wherein said output transducer is disposed facing in a direction opposite said first direction.

17. The method of claim 14, wherein said second input transducer and said output transducer are disposed in substantially the same plane.

18. The method of claim 17, wherein said second input transducer and said output transducer are both disposed facing in the same direction.

19. The method of claim 14, wherein said first input transducer, said second input transducer, and said output transducer are disposed in substantially the same plane.

20. The method of claim 19, wherein said first input transducer is disposed facing in a first direction and wherein said output transducer is disposed facing in a direction opposite said first direction and wherein said output transducer is also disposed facing in said direction opposite said first direction.