Hands free noise canceling headset

• US 5,699,436 A
• Filed: 10/27/1994
• Issued: 12/16/1997
• Est. Priority Date: 04/30/1992
• Status: Expired due to Fees

• Current Assignee: Noise Cancellation Technologies, Inc. (NCT Group, Inc.)
• Original Assignee: Noise Cancellation Technologies, Inc. (NCT Group, Inc.)
• Inventors: Denenberg, Jeffrey N., Claybaugh, David
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): HARVEY, MINSUN OH
• Application Number:
  US08/325,397
• Time in Patent Office: 1,146 Days
• Field of Search: 381/71, 381/72, 381/74, 381/94, 381/103, 381/155, 181/206, 379/406, 379/407, 379/410, 379/412, 379/387, 379/388, 379/390, 379/395
• US Class Current: 381/71.6
• CPC Class Codes: A61F 11/145 electric, e.g. for active noise reduction
• 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 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17875 using an error signal without a reference signal, e.g. pure feedback
• 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 2210/3028 Filtering, e.g. Kalman filters or special analogue or digital filters

Abstract

In the area of active noise cancellation headsets, the noisy environment often encountered in the link with communication systems causes lack of intelligibility on the outward communications path. Consequently another in-wire cancellation channel to enhance the intelligibility is required. This additional processing channel adds to the cost of the headset. The invention uses residual microphones (12) to reproduce the sound that remains in the ear after cancellation so that the controller (13) can make further adjustments through filter (15) and LMS adapter (14) to the anti-noise signal.

Claims

1. A hands-free active noise canceling headset comprising:

clamping means adapted to secure the headset to the users head,

at least one open back headset on said clamping means, said headset including a speaker means and a residual microphone means, and

a controller means operatively connected to said speaker means and

residual microphone means and adapted to both produce an anti-noise signal to said speaker means and adapted to receive signals from said residual microphone means representative of outward bound communications,

wherein said controller means includes

an LMS adapter, an adaptive filter means and an equalizer means to handle the anti-noise signals and communications signals from said residual

microphone means.

2. A headset as in claim 1 in which said controller means is adapted to develop a reference signal by subtracting an equalized anti-noise signal of its own from the residual signal.

3. An active noise canceling headset for blocking out selected noises while permitting two way-communication, said headset comprising:

at least one open backed headset means adapted to produce a residual signal, control, means adapted to generate an anti-noise signal and operatively connected to said open backed headset means, and

adaptive means within said control means adapted to produce a reference signal by subtracting an equalized version of its own anti-noise signal from the residual signal and produces an outward communication signal.

4. A headset as in claim 3 wherein said control means includes

a Least Means Square adaptation means which has inherent compensation for any effects of feedback delays around the control means.

5. A headset as in claim 4 wherein said open backed headset means includes two residual microphones adapted to produce in phase signals and the control means adds the signals generated by said two microphones which improves the signal to noise ratio as the in phase signals are in place.

6. A headset as in claim 3 wherein said control means includes an equalizer means, an adaptive filler means and a Least Mean Square adapter means.

7. A headset as in claim 4 where the headset means and the control means are connected by a wire means.