Classifications

• • G—PHYSICS
  • G10—MUSICAL INSTRUMENTS; ACOUSTICS
  • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
  • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
  • G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
  • G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R1/00—Details of transducers, loudspeakers or microphones
  • H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
  • H04R1/1083—Reduction of ambient noise
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R3/00—Circuits for transducers, loudspeakers or microphones
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R5/00—Stereophonic arrangements
  • H04R5/033—Headphones for stereophonic communication

Definitions

• the invention relates to noise cancellation systems, and is directed particularly, but not solely, towards a headphone noise cancellation system.
• Passenger vehicles particularly commercial aircraft, have seat installations which include appropriate connections, i.e. jacks for receiving connection plugs for headsets and headphones.
• the user either provides their own, or is provided with, a headset which the user plugs into the jack provided on the relevant seat to listen to various audio channels.
• headset and headphone are used interchangeably in this document since it is not relevant to the current invention whether a user microphone is fitted.
• the seat installation includes active noise cancellation electronic circuitry.
• the circuitry is operative to provide noise cancellation based on feedback from an appropriate sound transducer such as a microphone which is provided within the headset.
• the invention consists in a noise cancellation system having: a headphone including asound transducer and a headphone speaker, noise cancellation circuitry provided remote from the headphone, supplying the headphone speaker, and being supplied from the sound transducer, a filter to normalise the output from the sound transducer of the headphone to the noise cancellation circuitry.
• the filter is located at the output of the sound transducer to enable effective noise cancellation to be achieved in use.
• the filter comprises a passive electronic filter.
• the filter comprises a resistor/capacitor network.
• the filter is a high pass filter in parallel with the sound transducer.
• the sound transducer comprises an electret condenser microphone.
• the invention consists in a headphone for a noise cancellation system, the headphone including, one or more headphone speakers for providing sound to a user. at least one sound transducer provided in the headset adjacent to the speaker, and the output of the sound transducer being provided as an electrical signal and being provided to a filter, and the output of the filter being available to noise cancellation circuitry to cancel noise from the signal being delivered to the speaker.
• Figure 1 is a circuit schematic of a noise cancellation system according to the invention
• Figure 2 is a schematic of an equivalent circuit for a headset microphone and filter according to the invention
• Figure 3 is a schematic for one example of a practical implementation of the invention.
• the invention provides a way of allowing noise cancellation circuitry which is typically provided remote from a headphone, to be able to provide effective noise cancellation for a number of different headphone designs.
• This is achieved by providing the noise cancellation headphone sound transducer (typically a microphone such as an electret condenser microphone) with a passive filter so that the feedback signal provided by the microphone is appropriately conditioned for a "generic" active noise cancellation circuit or normalised.
• the invention allows the noise cancellation circuitry to be designed to be operative over a certain phase range of input feedback signals from a headset. This in turn means that a filter placed on the headset feedback signal may be appropriately configured for each different sort of headset so as to be acceptable to the noise cancellation circuitry and enable collective noise cancellation to be achieved.
• the filter comprises a simple passive filter.
• resistor/capacitor filter is a resistor/capacitor filter as described further below.
• simple resistor capacitor passive filter provides an appropriate transfer function that is suitable for active noise cancellation applications.
• This simple passive filter may have the values of resistance or capacitance varied dependent upon the nature of the headphone, the headphone sound transducer etc.
• the noise cancellation circuitry is shown generally referenced 6.
• the noise cancellation circuitry may be provided in a portable electronic device such as a portable audio system including those sold under the trade mark WALKMAN.
• the circuitry could alternatively be provided in a home stereo system, a television set or a variety of other devices which provide sound to a user.
• the noise cancellation circuitry 6 will be provided in a passenger vehicle. Again, a number of different forms of passenger transport may be provided so the noise cancellation circuitry may be provided in a seat installation
• the sound transducer for the headphone 4 is an electret condenser microphone 8, and the output of the microphone is provided to a passive filter network comprising resistor 10 and capacitor 12.
• the output from the passive filter network is referenced 14 and 16, and these outputs are typically provided as pins on a plug which is acceptable to an appropriate jack or socket on the device that includes the noise cancellation circuitry.
• the headset 4 also includes a speaker 18 which has input signal connections 20 and 22. Again, connections 20 and 22 are in use electrically connected to an appropriate plug pins (not shown) so that they can be supplied with an appropriate electrical signal from the output of the noise cancellation circuitry that is provided in the corresponding socket remote from the headphone.
• inputs 24 and 26 the input to the noise cancellation circuitry from the microphone is represented by inputs 24 and 26.
• Input 26 may be a reference such as ground
• input 24 is provided to an amplifier 28 via capacitor 30.
• the power supply VCC and bias resistor 32 are also provided.
• the output of amplifier 28 is fed to noise cancellation circuitry which may comprise a passive network or be active, for example being implemented using a microprocessor. Noise cancellation circuitry which may be used is not described in this document, as it is known to those skilled in the art.
• the output from the noise cancellation circuitry is provided to an appropriate output amplifier 34 to be provided to output terminals 36 and 26 which connect to terminals 20 and 22 for the headphone speaker.
• Figure 2 further explanation of the passive filter network described above is illustrated.
• the sound transducer 8 in the preferred form of the invention comprises an electret condenser microphone.
• This microphone behaves as a current source from a signal viewpoint.
• the microphone signal can be represented as a voltage source in series with the bias resistor, Rbias.
• the microphone signal is represented as voltage source 40, the output of which is in series with a bias resistor Rbias.
• the voltage source and bias resistor are in parallel with the passive filter comprising resistor 10 and capacitor 12.
• the network shown in Figure 2 provides a transfer function which is : 1 + sRC l + s(R + R bi as)C
• the headphone compensation is determined by targeting the noise cancellation at the best headphone to be catered for and then compensating other headphones to bring them to the same performance level.

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Circuit For Audible Band Transducer (AREA)
• Headphones And Earphones (AREA)
• Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

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Applications Claiming Priority (2)

Publications (1)

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Cited By (3)

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Citations (5)

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• 2003
  • 2003-06-26 DE DE10392880T patent/DE10392880T5/de not_active Withdrawn
  • 2003-06-26 GB GB0428314A patent/GB2406013B/en not_active Expired - Lifetime
  • 2003-06-26 JP JP2004517418A patent/JP2005531807A/ja active Pending
  • 2003-06-26 WO PCT/NZ2003/000134 patent/WO2004002383A1/en not_active Ceased
  • 2003-06-26 US US10/520,036 patent/US7489785B2/en not_active Expired - Fee Related
  • 2003-06-26 AU AU2003238975A patent/AU2003238975A1/en not_active Abandoned

Patent Citations (5)

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