Active noise cancellation aircraft headset system

• US 6,278,786 B1
• Filed: 07/29/1998
• Issued: 08/21/2001
• Est. Priority Date: 07/29/1997
• Status: Expired due to Term

• Current Assignee: Telex Communications Incorporated (Robert Bosch GmbH)
• Original Assignee: Telex Communications Incorporated (Robert Bosch GmbH)
• Inventors: McIntosh, Jason D.
• Primary Examiner(s): Mei, Xu
• Application Number:
  US09/124,686
• Time in Patent Office: 1,119 Days
• Field of Search: 381/71.1, 381/71.2, 381/71.3, 381/71.4, 381/71.5, 381/71.6, 381/71.7, 381/71.8, 381/71.9, 381/71.11, 381/71.12, 381/71.13, 381/71.14, 381/94.1, 381/94.2, 381/94.3, 381/94.7, 381/94.8, 381/94.9, 381/72, 381/73.1, 381/FOR.123, 381/FOR.124, 708/322
• US Class Current: 381/71.6
• CPC Class Codes: A61F 11/145 electric, e.g. for active noise reduction
• CPC Class Codes: G10K 11/17827 Desired external signals, e.g. pass-through audio such as music or speech
• 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 2210/1081 Earphones, e.g. for telephones, ear protectors or headsets
• CPC Class Codes: G10K 2210/1281 Aircraft, e.g. spacecraft, airplane or helicopter
• CPC Class Codes: G10K 2210/3013 Analogue, i.e. using analogue computers or circuits
• CPC Class Codes: G10K 2210/3026 Feedback
• CPC Class Codes: G10K 2210/3217 Collocated sensor and cancelling actuator, e.g. "virtual earth" designs
• CPC Class Codes: G10K 2210/511 Narrow band, e.g. implementations for single frequency cancellation
• CPC Class Codes: G10K 2210/512 Wide band, e.g. non-recurring signals
• 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

Abstract

An active noise cancellation aircraft headset system. A speaker is mounted within each earcup of a headset for receiving and acoustically transducing a composite noise cancellation signal. A microphone is also mounted within each earcup for transducing acoustic pressure within the earcup to a corresponding analog error signal. An analog filter receives the analog error signal and inverts it to generate an analog broadband noise cancellation signal. The analog error signal is also provided to an analog to digital converter, which receives the analog microphone error signal and converts it to a digital error signal. A DSP takes the digital error signal and, using an adaptive digital feedback filter, generates a digital tonal noise cancellation signal. A digital to analog converter then converts the digital tonal noise cancellation signal to an analog tonal noise cancellation signal so that it can be combined with the analog broadband noise cancellation signal. The resultant composite cancellation signal is provided to the speakers in the earcups to cancel noise within the earcups. The broadband analog cancellation is effective to reduce overall noise within the earcup, and the DSP not only provides active control of the analog cancellation loop gain to maximize the effectiveness of the broadband analog cancellation but also uses the adaptive feedback filter/algorithm to substantially reduce at least the loudest tonal noises penetrating the earcup, including engine and propeller noises, as well as harmonic vibrations of components of the aircraft'"'"'s fuselage.

Claims

1. An active noise cancellation aircraft headset system comprising:

an earcup;

a speaker mounted within the earcup for receiving and acoustically transducing a composite noise cancellation signal;

a microphone mounted within the earcup for transducing acoustic pressure within the earcup to a corresponding analog error signal;

an analog filter which receives the analog error signal and inverts it to generate an analog broadband noise cancellation signal;

an analog to digital converter which receives the analog error signal and converts it to a digital error signal;

a digital signal processor which receives the digital error signal and, using an adaptive digital feedback filter, generates a digital tonal noise cancellation signal;

a digital to analog converter which converts the digital tonal noise cancellation signal to an analog tonal noise cancellation signal;

summing means for receiving and summing the analog broadband noise cancellation signal and the analog tonal noise cancellation signal to generate the composite cancellation signal, the summing means providing the composite noise cancellation signal to the speaker to at least partially cancel aircraft noise within the earcup.

2. The headset system of claim 1 further comprising a variable gain amplifier which amplifies the analog broadband noise cancellation signal, the gain of the variable gain amplifier being controlled by the digital signal processor.

3. The headset system of claim 1 wherein the digital tonal noise cancellation signal corresponds to a tonal noise generated by an aircraft engine.

4. The headset system of claim 1 wherein the digital signal processor is disposed within a housing external to the earcup.

5. The headset system of claim 4 further comprising a signal conductive cord connecting components mounted in the earcup to components carried in the housing, the cord having a disconnectable plug permitting the earcup to be disconnected from the housing.

6. The headset system of claim 4 further comprising:

one or more additional headsets each having;

an earcup;

a speaker mounted within the earcup for receiving and acoustically transducing a composite noise cancellation signal; and

a microphone mounted within the earcup for transducing acoustic pressure within the earcup to a corresponding analog error signal;

a signal conductive cord connecting each such headset to the housing;

an analog filter for each such additional headset, each such analog filter receiving the analog error signal for such headset and inverting it to generate an analog broadband noise cancellation signal for such headset;

analog to digital converter means for receiving the analog error signal for each such additional headset and converting it to a digital error signal for such headset;

the digital signal processor receiving the digital error signal for each such additional headset and, using the adaptive feedback filter, generating a digital tonal noise cancellation signal for such headset;

digital to analog converter means for converting the digital tonal noise cancellation signal for each such headset to an analog tonal noise cancellation signal for such headset;

summing means for receiving and summing the analog broadband noise cancellation signal for each such additional headset and the analog tonal noise cancellation signal for each such additional headset to generate the composite cancellation signal for each such additional headset, the summing means providing each respective composite noise cancellation signal to the speaker of the corresponding headset to at least partially cancel aircraft noise within the earcup of such headset.

7. The headset system of claim 1 wherein the digital signal processor is disposed within the earcup.

8. A method of canceling noise within an earcup of an aircraft headset, comprising the steps of:

transducing acoustic pressure within the earcup, which acoustic pressure includes both tonal noise generated by an engine of an aircraft and other broadband aircraft noise, to generate an analog error signal;

providing the analog error signal to an analog filter which inverts it and generates an analog broadband noise cancellation signal;

providing the analog error signal to an analog to digital converter which converts the analog error signal to a digital error signal;

providing the digital error signal to a digital signal processor and, using an adaptive feedback filter, generating a digital tonal noise cancellation signal;

providing the digital tonal noise cancellation signal to a digital to analog converter which converts the digital tonal noise cancellation signal to an analog tonal noise cancellation signal;

summing the analog broadband noise cancellation signal and the analog tonal noise cancellation signal to generate a composite cancellation signal, and providing the composite noise cancellation signal to a speaker within the headset earcup, the speaker acoustically transducing the composite cancellation signal to reduce aircraft noise within the earcup.

9. A method of canceling noise within an earcup of an aircraft headset, comprising the steps of:

transducing acoustic pressure within the earcup, which acoustic pressure includes both tonal noise generated by an engine of an aircraft and other broadband aircraft noise, to generate an analog error signal;

inverting the analog error signal to generate an analog broadband noise cancellation signal;

converting the analog error signal to a digital error signal;

using a digital signal processor employing an adaptive feedback filter to generate a digital tonal noise cancellation signal based on the digital error signal;

converting the digital tonal noise cancellation signal to an analog tonal noise cancellation signal;

summing the analog broadband noise cancellation signal and the analog tonal noise cancellation signal to generate a composite cancellation signal; and

acoustically transducing the composite cancellation signal within the headset earcup to reduce the tonal and broadband aircraft noise within the headset earcup.

10. An active noise cancellation aircraft headset system comprising:

an earset including means for receiving and acoustically transducing an electronic composite noise cancellation signal, and means for transducing acoustic pressure within the earset to a corresponding analog error signal;

an analog filter which receives the analog error signal and inverts it to generate an analog broadband noise cancellation signal;

an analog to digital converter which receives the analog error signal and converts it to a digital error signal;

a digital signal processor which receives the digital error signal and, using an adaptive feedback filter, generates a digital tonal noise cancellation signal;

a digital to analog converter which converts the digital tonal noise cancellation signal to an analog tonal noise cancellation signal;

summing means for receiving and summing the analog broadband noise cancellation signal and the analog tonal noise cancellation signal to generate the composite cancellation signal, the summing means providing the composite noise cancellation signal to the means for receiving and acoustically transducing the composite noise cancellation signal.