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Active noise cancellation system

Info

Publication number
EP0539940B1
EP0539940B1 EP19920118416 EP92118416A EP0539940B1 EP 0539940 B1 EP0539940 B1 EP 0539940B1 EP 19920118416 EP19920118416 EP 19920118416 EP 92118416 A EP92118416 A EP 92118416A EP 0539940 B1 EP0539940 B1 EP 0539940B1
Authority
EP
Grant status
Grant
Patent type
Prior art keywords
noise
cancellation
signal
system
means
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.)
Expired - Lifetime
Application number
EP19920118416
Other languages
German (de)
French (fr)
Other versions
EP0539940A1 (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
Grant date

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Classifications

    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00Methods 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
    • G10K11/16Methods or devices for protecting against, or damping of, acoustic waves, e.g. sound
    • G10K11/175Methods or devices for protecting against, or damping of, acoustic waves, e.g. sound using interference effects; Masking sound
    • G10K11/178Methods or devices for protecting against, or damping of, acoustic waves, e.g. sound using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/10Applications
    • G10K2210/128Vehicles
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/301Computational
    • G10K2210/3039Nonlinear, e.g. clipping, numerical truncation, thresholding or variable input and output gain
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/301Computational
    • G10K2210/3045Multiple acoustic inputs, single acoustic output
    • GPHYSICS
    • G10MUSICAL INSTRUMENTS; ACOUSTICS
    • G10KSOUND-PRODUCING DEVICES; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K2210/00Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
    • G10K2210/30Means
    • G10K2210/301Computational
    • G10K2210/3046Multiple acoustic inputs, multiple acoustic outputs

Description

  • [0001]
    The present invention as it is defined in the appended claims 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.
  • [0002]
    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.
  • [0003]
    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. The document FR-A-2 531 023 discloses an active noise cancellation system to be used in motor vehicles.
  • [0004]
    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.
  • [0005]
    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 noise 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.
  • [0006]
    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.
  • [0007]
    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.
  • [0008]
    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.
EP19920118416 1991-10-31 1992-10-28 Active noise cancellation system Expired - Lifetime EP0539940B1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
FI915143A FI94563C (en) 1991-10-31 1991-10-31 active Noise Reduction System
FI915143 1991-10-31

Publications (2)

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

Family

ID=8533403

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19920118416 Expired - Lifetime EP0539940B1 (en) 1991-10-31 1992-10-28 Active noise cancellation system

Country Status (4)

Country Link
JP (1) JP3412846B2 (en)
DE (2) DE69210169D1 (en)
EP (1) EP0539940B1 (en)
FI (1) FI94563C (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8077873B2 (en) 2009-05-14 2011-12-13 Harman International Industries, Incorporated System for active noise control with adaptive speaker selection
US8135140B2 (en) 2008-11-20 2012-03-13 Harman International Industries, Incorporated System for active noise control with audio signal compensation
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
US8718289B2 (en) 2009-01-12 2014-05-06 Harman International Industries, Incorporated System for active noise control with parallel adaptive filter configuration
US9020158B2 (en) 2008-11-20 2015-04-28 Harman International Industries, Incorporated Quiet zone control system

Families Citing this family (4)

* 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
JP3410141B2 (en) * 1993-03-29 2003-05-26 富士重工業株式会社 Vehicle interior noise reduction device
US5692055A (en) * 1996-09-24 1997-11-25 Honda Giken Kogyo Kabushiki Kaisha Active noise-suppressive control method and apparatus
ES2143952B1 (en) * 1998-05-20 2000-12-01 Univ Madrid Politecnica active acoustic noise attenuator by genetic adaptive algorithm.

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04273B2 (en) * 1982-07-07 1992-01-06 Nissan Motor
FR2531023B1 (en) * 1982-08-02 1987-04-30 Peugeot Device for attenuation of the noise in the cabin of a motor vehicle

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8135140B2 (en) 2008-11-20 2012-03-13 Harman International Industries, Incorporated System for active noise control with audio signal compensation
US8270626B2 (en) 2008-11-20 2012-09-18 Harman International Industries, Incorporated System for active noise control with audio signal compensation
US8315404B2 (en) 2008-11-20 2012-11-20 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

Also Published As

Publication number Publication date Type
EP0539940A1 (en) 1993-05-05 application
DE69210169T2 (en) 1996-10-02 grant
FI94563B (en) 1995-06-15 application
FI915143D0 (en) grant
JPH05241581A (en) 1993-09-21 application
JP3412846B2 (en) 2003-06-03 grant
FI915143A0 (en) 1991-10-31 application
FI94563C (en) 1995-09-25 grant
FI915143A (en) 1993-05-01 application
DE69210169D1 (en) 1996-05-30 grant

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