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EP0539940A1 - Active noise cancellation system - Google Patents

Active noise cancellation system Download PDF

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Publication number
EP0539940A1
EP0539940A1 EP92118416A EP92118416A EP0539940A1 EP 0539940 A1 EP0539940 A1 EP 0539940A1 EP 92118416 A EP92118416 A EP 92118416A EP 92118416 A EP92118416 A EP 92118416A EP 0539940 A1 EP0539940 A1 EP 0539940A1
Authority
EP
European Patent Office
Prior art keywords
noise
cancellation
signal
generating
target area
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP92118416A
Other languages
German (de)
French (fr)
Other versions
EP0539940B1 (en
Inventor
Juha Kuusama
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nokia Technology GmbH
Original Assignee
Nokia Technology GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nokia Technology GmbH filed Critical Nokia Technology GmbH
Publication of EP0539940A1 publication Critical patent/EP0539940A1/en
Application granted granted Critical
Publication of EP0539940B1 publication Critical patent/EP0539940B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • G10K11/1781—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 characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
    • G10K11/17821—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 characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the input signals only
    • G10K11/17823—Reference signals, e.g. ambient acoustic environment
    • 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
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17853—Methods, e.g. algorithms; Devices of the filter
    • G10K11/17854—Methods, e.g. algorithms; Devices of the filter the filter being an adaptive filter
    • 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
    • G10K11/1787—General system configurations
    • G10K11/17879—General system configurations using both a reference signal and an error signal
    • G10K11/17881—General system configurations using both a reference signal and an error signal the reference signal being an acoustic signal, e.g. recorded with a microphone
    • 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10—Applications
    • G10K2210/128—Vehicles
    • 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3039—Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain
    • 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3045—Multiple acoustic inputs, single acoustic output
    • 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
    • G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30—Means
    • G10K2210/301—Computational
    • G10K2210/3046—Multiple acoustic inputs, multiple acoustic outputs

Definitions

  • the present invention relates to an active noise cancellation system for a motor vehicle, comprising means for generating one or more electrical signals proportional to the noise in the target area, an electronic means receiving these signals, such as an adaptive filter, for generating a cancellation noise signal, one or more sound sources connected to said electronic means for generating cancellation noise in the target area, and one or more sensors for detecting residual noise in the target area and transmitting it in an electrical form to the electronic means to tune its operation.
  • FIG. 1 in the accompanying drawings represents schematically the main principle of an active noise cancellation system
  • Figure 2 shows a block diagram corresponding to this basic schematic drawing.
  • a conventional system for active noise cancellation of the kind shown in Figure 1 comprises noise detection sensors 1 generating an electrical signal proportional to the noise present in the target area.
  • These detection sensors can be either microphones, in which case the signal generated by them corresponds to the noise in the target area, or the detection sensors may also be of another type, in which case they generate for instance only a reference signal proportional to the rotation speed of the vehicle motor.
  • the signals generated by the detection sensors 1 need not correspond to the actual noise, but only be correlated with it.
  • These detection sensor signals are conveyed to an electronic means 2 generating a noise cancellation signal, which most commonly is an adaptive filter.
  • This adaptive filter calculates by means of a suitable algorithm, such as an LMS algorithm or a Fan-Vemuri algorithm, a signal which in amplitude corresponds to the produced noise signal but is of an opposite phase thereto.
  • a suitable algorithm such as an LMS algorithm or a Fan-Vemuri algorithm
  • Such a cancellation noise signal is reproduced by cancellation noise sources, such as loudspeakers 3, to generate cancellation noise in the target area. Attenuation of the noise is achieved as a combined result of the actual noise and the cancellation noise of an opposite phase.
  • noise can be cancelled by such an arrangement about 10 -30 dB for instance at the motor noise frequency.
  • the system further comprises residual noise sensors 4 which have been adapted to detect residual noise in the target area and control the means 2 for generating the cancellation noise in response to this.
  • FIG 2 shows a block diagram corresponding to the system of Figure 1.
  • the signal generated by the noise detection sensor 1 has been denoted by the reference character x, which signal is inputted in a means 2 for generating a cancellation noise signal, which generates a signal y that is a function of the noise signal x.
  • This signal y is then reproduced by a loudspeaker 3, in which situation the signal proceeds as a sound wave via a transmission route H to a sensor 4 for residual noise.
  • This sensor 4 for residual noise which may in practice be for instance a microphone, generates an electrical signal e which may be represented as a function H(y)+n, wherein n is noise in the microphone 4.
  • the system of the invention which is characterized in that an amplifier has been disposed between the sound source or sources of cancellation noise and the means for generating a cancellation noise signal to control the gain of the cancellation noise signal in response to a signal proportional to the rotation speed of the vehicle motor.
  • the stability problem has now been solved by varying the gain of the cancellation noise signal in dependence on the frequency and specifically in dependence on the rotation speed of the vehicle motor.
  • the gain of the cancellation noise signal is increased when the rotation speed of the motor decreases.
  • Figure 3 represents a block diagram of the sound cancellation system of the invention, wherein an additional amplifier 5 has been disposed between the sound source of cancellation noise 3 and the means 2 for generating the cancellation noise signal, said additional amplifier being controlled as a function of the signal z.
  • this signal z is proportional to the rotation speed of the vehicle motor.
  • the gain of the signal y generated by the amplifier 5 is an inverse function of the frequency of this signal z.
  • the gain of the amplifier 5 is reduced, and respectively as the frequency of the signal z decreases, i.e. the rotation speed of the vehicle motor decreases, the gain is boosted.
  • Increasing the gain at low frequencies is necessary in order for the loudspeaker 3 to be able to reproduce also these frequencies with a sufficient amplitude.
  • the gain of the amplifier 5 and specifically its variation as a function of the frequency of signal z must be adapted to the practical conditions prevailing in each case.
  • the essential feature is that the gain of the amplifier 5 is controlled in dependence on the rotation speed of the vehicle motor.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)

Abstract

The invention relates to an active noise cancellation system for a motor vehicle, comprising means (1) for generating one or more electrical signals proportional to the noise in the target area, an electronic means (2) receiving these signals, such as an adaptive filter, for generating a cancellation noise signal, one or more sound sources (3) connected to said electronic means for generating cancellation noise in the target area, and one or more sensors (4) for detecting residual noise in the target area and transmitting it in an electrical form to the electronic means (2) to tune its operation. To enhance the operation of the system, an amplifier (5) has been disposed between the sound source or sources (3) of cancellation noise and the means (2) for generating a cancellation noise signal to control the gain of the cancellation noise signal in response to a signal (z) proportional to the rotation speed of the vehicle motor.

Description

  • The present invention relates to an active noise cancellation system for a motor vehicle, comprising means for generating one or more electrical signals proportional to the noise in the target area, an electronic means receiving these signals, such as an adaptive filter, for generating a cancellation noise signal, one or more sound sources connected to said electronic means for generating cancellation noise in the target area, and one or more sensors for detecting residual noise in the target area and transmitting it in an electrical form to the electronic means to tune its operation.
  • Figure 1 in the accompanying drawings represents schematically the main principle of an active noise cancellation system, and Figure 2 shows a block diagram corresponding to this basic schematic drawing. A conventional system for active noise cancellation of the kind shown in Figure 1 comprises noise detection sensors 1 generating an electrical signal proportional to the noise present in the target area. These detection sensors can be either microphones, in which case the signal generated by them corresponds to the noise in the target area, or the detection sensors may also be of another type, in which case they generate for instance only a reference signal proportional to the rotation speed of the vehicle motor. Thus the signals generated by the detection sensors 1 need not correspond to the actual noise, but only be correlated with it. These detection sensor signals are conveyed to an electronic means 2 generating a noise cancellation signal, which most commonly is an adaptive filter. This adaptive filter calculates by means of a suitable algorithm, such as an LMS algorithm or a Fan-Vemuri algorithm, a signal which in amplitude corresponds to the produced noise signal but is of an opposite phase thereto. Such a cancellation noise signal is reproduced by cancellation noise sources, such as loudspeakers 3, to generate cancellation noise in the target area. Attenuation of the noise is achieved as a combined result of the actual noise and the cancellation noise of an opposite phase. In practice, noise can be cancelled by such an arrangement about 10 -30 dB for instance at the motor noise frequency. In order that the means for generating the cancellation noise signal may be effectively controlled and adapted to the conditions in each case, the system further comprises residual noise sensors 4 which have been adapted to detect residual noise in the target area and control the means 2 for generating the cancellation noise in response to this.
  • Figure 2 shows a block diagram corresponding to the system of Figure 1. Therein the signal generated by the noise detection sensor 1 has been denoted by the reference character x, which signal is inputted in a means 2 for generating a cancellation noise signal, which generates a signal y that is a function of the noise signal x. This signal y is then reproduced by a loudspeaker 3, in which situation the signal proceeds as a sound wave via a transmission route H to a sensor 4 for residual noise. This sensor 4 for residual noise, which may in practice be for instance a microphone, generates an electrical signal e which may be represented as a function H(y)+n, wherein n is noise in the microphone 4.
  • In practice, it has been found that the degree of cancellation achieved by the systems of Figures 1 and 2 is greatly dependent on the amplitude gain of H(y). This gain dependence leads in practice to such a situation that a system of the kind described in Figure 2 is only stable with specific gains and even so that the gains that are available are greatly dependent on the frequency band in which one wishes the active noise cancellation to be the most effective.
  • Thus a problem is encountered with tuning the control system so as to operate effectively in different frequency bands without presenting problems in the operation of the system. This is achieved with the system of the invention, which is characterized in that an amplifier has been disposed between the sound source or sources of cancellation noise and the means for generating a cancellation noise signal to control the gain of the cancellation noise signal in response to a signal proportional to the rotation speed of the vehicle motor. Thus the stability problem has now been solved by varying the gain of the cancellation noise signal in dependence on the frequency and specifically in dependence on the rotation speed of the vehicle motor. Preferably the gain of the cancellation noise signal is increased when the rotation speed of the motor decreases. Even though the amplitude of the noise prevailing in the vehicle actually decreases when the rotation speed of the motor decreases simultaneously as the frequency of the nose decreases, yet in that case the gain must be increased on account of the practical limitations presented by the smallness of the interior of the vehicle and the properties of the sound sources available. Conventional loudspeakers reproduce low frequencies rather poorly, and the dimensions of the reproduction space also have a significant effect of restricting the possibility of reproduction of low frequencies.
  • In the following, the system of the invention will be described in more detail with reference to the enclosed drawing, wherein
    • Figure 1 shows schematically the principle of construction of an active sound cancellation system,
    • Figure 2 shows a block diagram corresponding to the system of Figure 1, and
    • Figure 3 shows a block diagram of the sound cancellation system of the invention.
  • Figure 3 represents a block diagram of the sound cancellation system of the invention, wherein an additional amplifier 5 has been disposed between the sound source of cancellation noise 3 and the means 2 for generating the cancellation noise signal, said additional amplifier being controlled as a function of the signal z. In accordance with the invention, this signal z is proportional to the rotation speed of the vehicle motor. Preferably the gain of the signal y generated by the amplifier 5 is an inverse function of the frequency of this signal z. Thus, as the frequency of the signal z increases the gain of the amplifier 5 is reduced, and respectively as the frequency of the signal z decreases, i.e. the rotation speed of the vehicle motor decreases, the gain is boosted. Increasing the gain at low frequencies is necessary in order for the loudspeaker 3 to be able to reproduce also these frequencies with a sufficient amplitude.
  • When an amplifier 5 providing a gain inversely correlated with the frequency of the principal source of noise for the cancellation of which the system is intended is incorporated into the system, problems related to the instability of the control system are avoided and the level of noise cancellation can be substantially enhanced. In order for optimum operation to be achieved in each use application, the gain of the amplifier 5 and specifically its variation as a function of the frequency of signal z must be adapted to the practical conditions prevailing in each case. However, the essential feature is that the gain of the amplifier 5 is controlled in dependence on the rotation speed of the vehicle motor.

Claims (2)

  1. An active noise cancellation system for a motor vehicle, comprising means (1) for generating one or more electrical signals proportional to the noise in the target area, an electronic means (2) receiving these signals, such as an adaptive filter, for generating a cancellation noise signal, one or more sound sources (3) connected to said electronic means for generating cancellation noise in the target area, and one or more sensors (4) for detecting residual noise in the target area and transmitting it in an electrical form to the electronic means (2) to tune its operation, characterized in that an amplifier (5) has been disposed between the sound source or sources (3) of cancellation noise and the means (2) for generating a cancellation noise signal to control the gain of the cancellation noise signal in response to a signal (z) proportional to the rotation speed of the vehicle motor.
  2. A system as claimed in claim 1, characterized in that the gain of the amplifier (5) is inversely proportional to the frequency of the signal (z) controlling it.
EP92118416A 1991-10-31 1992-10-28 Active noise cancellation system Expired - Lifetime EP0539940B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI915143 1991-10-31
FI915143A FI94563C (en) 1991-10-31 1991-10-31 Active noise canceling system

Publications (2)

Publication Number Publication Date
EP0539940A1 true EP0539940A1 (en) 1993-05-05
EP0539940B1 EP0539940B1 (en) 1996-04-24

Family

ID=8533403

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92118416A Expired - Lifetime EP0539940B1 (en) 1991-10-31 1992-10-28 Active noise cancellation system

Country Status (4)

Country Link
EP (1) EP0539940B1 (en)
JP (1) JP3412846B2 (en)
DE (1) DE69210169T2 (en)
FI (1) FI94563C (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2276793A (en) * 1993-03-29 1994-10-05 Fuji Heavy Ind Ltd Vehicle internal noise reduction system
GB2265277B (en) * 1992-03-17 1996-07-24 Fuji Heavy Ind Ltd Noise reduction system for automobile compartment
US5692055A (en) * 1996-09-24 1997-11-25 Honda Giken Kogyo Kabushiki Kaisha Active noise-suppressive control method and apparatus
ES2143952A1 (en) * 1998-05-20 2000-05-16 Univ Madrid Politecnica Active attenuator of acoustic noise using a genetic adaptive algorithm

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004006604B4 (en) * 2004-02-11 2020-03-12 Volkswagen Ag Device and method for reducing noise in the interior of a motor vehicle
US8135140B2 (en) 2008-11-20 2012-03-13 Harman International Industries, Incorporated System for active noise control with audio signal compensation
US9020158B2 (en) 2008-11-20 2015-04-28 Harman International Industries, Incorporated Quiet zone control system
US8718289B2 (en) 2009-01-12 2014-05-06 Harman International Industries, Incorporated System for active noise control with parallel adaptive filter configuration
US8189799B2 (en) 2009-04-09 2012-05-29 Harman International Industries, Incorporated System for active noise control based on audio system output
US8199924B2 (en) 2009-04-17 2012-06-12 Harman International Industries, Incorporated System for active noise control with an infinite impulse response filter
US8077873B2 (en) 2009-05-14 2011-12-13 Harman International Industries, Incorporated System for active noise control with adaptive speaker selection
EP3245650B1 (en) * 2016-04-06 2018-08-15 Eberspächer Exhaust Technology GmbH & Co. KG System and method for active sound influencing

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0098594A2 (en) * 1982-07-07 1984-01-18 Nissan Motor Co., Ltd. A method and apparatus for controlling the sound field in a vehicle cabin or the like
FR2531023A1 (en) * 1982-08-02 1984-02-03 Peugeot Noise attenuation device in the passenger compartment of an automobile vehicle.

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0098594A2 (en) * 1982-07-07 1984-01-18 Nissan Motor Co., Ltd. A method and apparatus for controlling the sound field in a vehicle cabin or the like
FR2531023A1 (en) * 1982-08-02 1984-02-03 Peugeot Noise attenuation device in the passenger compartment of an automobile vehicle.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MACHINE DESIGN, vol. 59, no. 29, 10th December 1987, page 70, Cleveland, Ohio, US; ANONYMOUSLY: "Low-frequency noise gets waved back" *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2265277B (en) * 1992-03-17 1996-07-24 Fuji Heavy Ind Ltd Noise reduction system for automobile compartment
GB2276793A (en) * 1993-03-29 1994-10-05 Fuji Heavy Ind Ltd Vehicle internal noise reduction system
GB2276793B (en) * 1993-03-29 1996-12-18 Fuji Heavy Ind Ltd Vehicle internal noise reduction system
US5692055A (en) * 1996-09-24 1997-11-25 Honda Giken Kogyo Kabushiki Kaisha Active noise-suppressive control method and apparatus
ES2143952A1 (en) * 1998-05-20 2000-05-16 Univ Madrid Politecnica Active attenuator of acoustic noise using a genetic adaptive algorithm

Also Published As

Publication number Publication date
FI94563B (en) 1995-06-15
FI915143A (en) 1993-05-01
DE69210169D1 (en) 1996-05-30
EP0539940B1 (en) 1996-04-24
DE69210169T2 (en) 1996-10-02
FI915143A0 (en) 1991-10-31
JPH05241581A (en) 1993-09-21
JP3412846B2 (en) 2003-06-03
FI94563C (en) 1995-09-25

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