WO1994029847A1 - Suppression active du bruit dans un espace tridimensionnel - Google Patents

Suppression active du bruit dans un espace tridimensionnel Download PDF

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Publication number
WO1994029847A1
WO1994029847A1 PCT/US1994/004901 US9404901W WO9429847A1 WO 1994029847 A1 WO1994029847 A1 WO 1994029847A1 US 9404901 W US9404901 W US 9404901W WO 9429847 A1 WO9429847 A1 WO 9429847A1
Authority
WO
WIPO (PCT)
Prior art keywords
noise
microphone
sound
signal
input
Prior art date
Application number
PCT/US1994/004901
Other languages
English (en)
Inventor
Sen M. Kuo
Mary K. Christensen
Robert A. Herold
Original Assignee
Caterpillar Inc.
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 Caterpillar Inc. filed Critical Caterpillar Inc.
Priority to AU68248/94A priority Critical patent/AU6824894A/en
Publication of WO1994029847A1 publication Critical patent/WO1994029847A1/fr

Links

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
    • G10K11/1787—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
    • 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
    • G10K11/1785—Methods, e.g. algorithms; Devices
    • G10K11/17857—Geometric disposition, e.g. placement of microphones
    • 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
    • G10K2210/103—Three dimensional
    • 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
    • G10K2210/12—Rooms, e.g. ANC inside a room, office, concert hall or automobile cabin
    • 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
    • G10K2210/3012—Algorithms
    • 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
    • G10K2210/3019—Cross-terms between multiple in's and out's
    • 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
    • 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
    • G10K2210/321—Physical
    • G10K2210/3219—Geometry of the configuration

Definitions

  • the invention relates to the control of sound using active noise cancellation and in particular to the formation of a localized three dimensional quiet zone with a reduced sound level.
  • Active noise cancellation involves superimposing on a noise acoustic wave an opposite acoustic wave that destructively interferes with and cancels the noise wave.
  • the cancelling acoustic wave is of equal amplitude but of opposite phase to the noise acoustic wave.
  • the generation of the proper interference signal to produce cancellation, in the proper position at the right time, requires talcing into consideration a number of variables resulting in elaborate signal processing.
  • the active noise cancellation principle is most useful at frequencies below 500 cycles per second (Hz) . Above that frequency range, noise attenuating materials applied to surfaces are more effective.
  • the implementation of the principle of active noise cancellation generally involves sensing of the characteristics of the noise acoustic wave, generating the cancelling acoustic wave and through monitoring the combined waves developing a feedback signal that keeps the cancelling wave in adjustment.
  • the monitoring signal is frequently called an "error" signal.
  • Active noise cancellation systems exhibit instability under conditions where the cancelling signal gets into the noise prior to the sensing of the characteristics of that noise. Care in constructing a system is employed to prevent the situation or a modification of the algorithm can be used to accommodate it.
  • the invention provides a localized region where the level of sound is controlled, that is three dimensional, and is of a size suitable as the workplace of an operator.
  • the controlled sound region is achieved by projecting an active noise cancelling signal into a localized region in the area with the background noise.
  • An input to the cancelling signal is the product of a collection of individual noises that are part of the background noise each of which individual noises is collected acoustically at a location proximate to the source of the individual noise component, by placing at least one of a plurality of individual microphones adjacent each source of component noise.
  • the cancelling signal is monitored by microphones placed in the controlled sound region and the cancelling signal is maintained in effectiveness by processing that performs the special functions of normalization of multiple inputs and in an adaptive filtering type algorithm accommodation of multiple cancellation signal speakers and prevention of component saturation.
  • Figure 1 is a schematic view of the sound control system of the invention.
  • Figures 2, 3 and 4 are cryptic sketches of the remote acoustic sensing of exemplary individual types of sources of noise that make up the background noise.
  • Figure 5 is a sketch illustrating the acoustic paths and electrical component wiring of the invention.
  • Figure 6 is a diagram of a functional block representation of the algorithm employed in processing the active noise cancellation signal.
  • the invention involves structural and processing modifications that permit the principle of active noise cancellation to be used in producing a three dimensional quiet zone in a noisy area that has a size suitable for an individual such as an equipment operator. While the shape of the quiet zone and the amount of sound level reduction in it may be affected by complex sound fields involving speaker positioning frequency of the noise being cancelled and reflection from nearby objects; the quiet zone should have at least a theoretical lOdB sound level reduction within an essentially spheroidal shape with a diameter about 1/5 of the wavelength of the particular noise frequency. Expressed another way, the at least lOdB reduction or about 1/100 of the mean square pressure of the primary noise source, should extend about 0.1 of the wavelength from the centerpoint of cancellation.
  • the quiet zone is about the size of the head and shoulders of an equipment operator.
  • the invention is particularly useful in construction equipment, wherein the primary noise source is the equipment's drivetrain (not shown) .
  • the invention includes a means 29 for reducing the sound level in the quiet zone which is a result of the primary noise source.
  • the primary noise reducing means includes an acoustic input or primary microphone 30 located generally in the vicinity of the drivetrain and particularly within an enclosure of the drivetrain.
  • the primary noise may be sensed by other types of sensors, e.g., tachometers.
  • the invention is particularly valuable in controlling low frequency, up to 500 cycles per second (Hz) sound. At those low frequencies, passive sound barriers are minimally effective.
  • the structural modifications involve the positioning of the speakers or cancelling signal transducers; the positioning of the monitoring microphones or error transducers; and the positioning of the sensing or input microphones for acoustic sensing of sounds, that are components of the background noise, at the location of the source of that sound.
  • FIG. 1 there is shown a schematic view of the sound control system of the invention wherein in a space 1 surrounded by background sound 2, shown with dashed lines, a quiet zone, or zone of reduced sound level 3 is produced by projecting into the zone 3 that is to be quiet an active noise cancellation signal through an acoustic transducer means shown in this illustration as speakers 4 and 5.
  • the active noise cancellation signal is monitored through a monitoring sound pickup means shown in this illustration as microphones 6 and 7.
  • the background sound 2 is made up of at least one and often several sources of sound with the location of the sources being outside the area of the quiet region and usually outside of an enclosure not shown.
  • the active noise cancellation signal projected by the speakers 4 and 5 is a signal designed to cancel the primary noise and the selected component noises sound frequencies in the background noise 2.
  • the monitoring or error signal sensing is accomplished with microphones 6 and 7 positioned in the quiet zone 3 generally close to the location of the ears of the operator.
  • a processor 8 is provided that performs the mathematical operations and signal generating operations required in translating the monitoring and input signals into a constantly updated cancellation signal.
  • the input sounds are acoustically sensed at positions that are proximate to the sources of those sounds. In this illustration three, 9, 10 and 11 are shown that would pick up the sound at the source of origination from such items as running machinery and air conditioning pumps.
  • the speakers 4 and 5 and the microphones 6 and 7 are connected to the processor 8 by conductors 14, 15, 16 and 17, respectively.
  • the system removes from the background sound as many component sounds as practical while permitting the operator or occupant of the quiet zone the freedom to move and the ability to hear the sounds necessary such as emergency indications.
  • signals indicating the condition of the cancelling signal being projected into the quiet zone 3 are transmitted by the monitoring or error microphones through conductors 16 and 17 to the processor 8.
  • the processor 8 processes and normalizes the input signals from the selected sources of noise to be cancelled delivered through microphones 9, 10 and 11.
  • the processor also processes the signals from the monitoring microphones using an adaptive least means squared type of algorithm known in the art with modifications to accommodate several cancelling speakers to improve stepping in developing filter values and to prevent component saturation in developing a constantly updated cancellation signal, which is delivered to the speakers 4 and 5 through conductors 14 and 15.
  • the quiet zone 3 is about the size of the head and shoulders of a human, shown dotted in Figure 1.
  • the zone 3 can be positioned by selecting the location of the speakers 4 and 5 so that the operator would not be confined to a particular standing or sitting type of position.
  • the monitoring microphones are positioned in the quiet zone in the vicinity of where the ears of the operator are likely to be.
  • An aspect of the invention is the sensing of sound outside the area of the background sound region where the operator must work to reduce the sound level in the quiet zone 3.
  • 3 and 4 cryptic sketches are provided of the remote acoustic sensing of three different types of sound sources.
  • the noise components usually desired to be removed are those that raise the general level but have a low probability of containing information useful to the operator.
  • the input microphone is positioned close to the source of the sound but the sound travels through the air to the microphone.
  • indirect sound indicators such as tachometers and ignition pulse counters have been used. It has been found that acoustic pickup not only cancels harmonics but also can cancel broad background noise and is a more faithful replica of what the ear would hear.
  • Fig. 2 the sound of a liquid in a pipe 18 in a remote location symbolized by a wall portion of an enclosure is shown with the pick up microphone 9 being separated by air from the pipe 18.
  • a sound source having a steady noise of a conveyor 19 and an intermittent percussive noise of a stamping operation 12 is shown separated by an enclosure again symbolized by a wall and with the pick up microphone 10 separated by air from the sound sources.
  • Fig. 4 the sound of rotating machinery 21 located in a location remote from the quiet zone region is illustrated. In this illustration as in the others the pickup microphone 11 is separated by air from the source 21. The sensing of the input noise from source locations that are remote also reduces any acoustic feedback from the cancelling signal and permits the effect from having to be taken into consideration in the algorithm.
  • Figure 5 wherein a sketch is shown illustrating the acoustic paths and electrical component wiring in the invention.
  • Fig. 5 the acoustic paths between the speakers 4 and 5 and the monitoring microphones 6 and 7 are shown as dash-dot lines to illustrate that where there is more than one cancelling speaker and more than one monitoring microphone the algorithm in the controller 20 of the processor 8 must accommodate the fact that each monitoring microphone will receive input from each speaker.
  • the processor 8 for the monitoring microphone signals enter the controller 20.
  • an input signal normalization stage consisting of an input signal normalization stage consisting of a summing amplifier 23, and input operational or reference amplifiers 24, 25, 26 and 31 for the remotely sensed noise signals from microphones 9, 10 and 11 and for the primary noise sensing means 29, respectively.
  • controller 20 stage of the processor 8 there is an adaptive least means squares type of algorithm embodied in integrated circuit form.
  • the output stages 27 and 28 deliver the cancelling signal from the controller 20 through conductors 14 and 15 to the speakers 4 and 5 respectively.
  • controller 20 is a commercially available integrated circuit.
  • a satisfactory model for controller 20 is the TMS 320C30 Floating Point DSP manufactured by Texas Instruments, Inc., Dallas, Texas.
  • a satisfactory model of a microphone suitable for an input microphone is a model PZM distributed by the Radio Shack Co.; and a satisfactory model of a micrphone suitable for a monitoring microphone is a model SM98A made by the SHURE, CO.
  • a satisfactory model of a cancelling speaker is the Rockford Fosgate PR0128 12" Subwoofer.
  • a satisfactory algorithm is the Multi Channel Filtered X Least Mean Squares type with modifications to accommodate multiple speakers component saturation and small steps.
  • a preferred embodiment example is shown in Fig. 6.
  • FIG. 6 there is shown a diagram of a functional block representation of the algorithm employed in processing the elements of the active noise cancellation signal of the invention.
  • the algorithm is the Multi Channel Filtered X Least Mean Squares type known in the art with the modifications of the invention.
  • the elements represent the functions of variables that influence the cancelling signal and the monitor or error signals.
  • the algorithm operates by calculating an error correction for the cancelling signal, applying the correction and repeating in a series of cycles till a minimum variation is achieved.
  • the selected input noise signals delivered through terminals 9, 10 and 11 have been normalized by providing weighting factors for the input microphone paths and algebraically adding them in a summing amplifier as shown in Fig. 5 and the combined signal enters the algorithm as a normalized input.
  • the cancelling signal as shown from the acoustic paths in Figure 5 travels in the main paths directly from the speakers to the monitoring microphones 6 and 7.
  • the adaptive filters of the controller provide adjustment of the cancellation signals. A portion of each signal in the acoustic path goes direct to the nearest microphone and across to the other microphone.
  • the main, the direct from cancellation signal 1, and the cross from cancellation signal 2 are acoustically superimposed to form error signal 1, which in turn, is introduced into the controller labelled FILTERED X LMS.
  • FILTERED X LMS A similar situation takes place to produce error signal 2.
  • the changes in the adaptive filter as the iteration steps take place is indicated by a dashed arrow.
  • the size of the steps taken will influence how soon the algorithm will converge on the optimum minimum error in the cancelling signal.
  • the weight vector is changed every iteration.
  • the step size is influenced by input signal and error signal power.
  • the algorithm accommodates in the filter weighting for the multiple paths from the speakers to the monitoring microphone

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

L'invention concerne une zone délimitée, tridimensionnelle sans bruit (3) convenant au poste de travail (4) d'un opérateur. Un signal actif de suppression du bruit est projeté dans la zone (3), où sont présents des microphones d'écoute (6, 7). Le son entrant est détecté acoustiquement aux sources d'une pluralité de sources sonores et il est normalisé. La suppression active du bruit est ajustée par un algorithme adaptatif X filtré avec prises en compte de l'existence de microphones d'écoute multiples (6, 7) et de haut-parleurs multiples (4, 5).
PCT/US1994/004901 1993-06-11 1994-05-02 Suppression active du bruit dans un espace tridimensionnel WO1994029847A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU68248/94A AU6824894A (en) 1993-06-11 1994-05-02 Three dimensional sound control with active noise cancellation

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US7450693A 1993-06-11 1993-06-11
US08/074,506 1993-06-11

Publications (1)

Publication Number Publication Date
WO1994029847A1 true WO1994029847A1 (fr) 1994-12-22

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PCT/US1994/004901 WO1994029847A1 (fr) 1993-06-11 1994-05-02 Suppression active du bruit dans un espace tridimensionnel

Country Status (2)

Country Link
AU (1) AU6824894A (fr)
WO (1) WO1994029847A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008129022A1 (fr) * 2007-04-24 2008-10-30 Anocsys Ag Arrangement et procédé avec un système de réduction du bruit actif
FR2999772A1 (fr) * 2012-12-19 2014-06-20 Ixblue Procede de controle actif acoustique de bruit perturbateur a bande(s) etroite(s) a microphone(s) mobile(s), systeme correspondant

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111785243B (zh) * 2020-06-10 2024-02-09 厦门市派美特科技有限公司 一种耳机有源降噪方法及系统

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0434468A2 (fr) * 1989-12-22 1991-06-26 Bridgestone Corporation Dispositif de commande de vibrations
GB2257601A (en) * 1991-07-09 1993-01-13 Honda Motor Co Ltd Active vibration control system
GB2271908A (en) * 1992-10-21 1994-04-27 Lotus Car Adaptive control for a noise cancelling system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0434468A2 (fr) * 1989-12-22 1991-06-26 Bridgestone Corporation Dispositif de commande de vibrations
GB2257601A (en) * 1991-07-09 1993-01-13 Honda Motor Co Ltd Active vibration control system
GB2271908A (en) * 1992-10-21 1994-04-27 Lotus Car Adaptive control for a noise cancelling system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008129022A1 (fr) * 2007-04-24 2008-10-30 Anocsys Ag Arrangement et procédé avec un système de réduction du bruit actif
FR2999772A1 (fr) * 2012-12-19 2014-06-20 Ixblue Procede de controle actif acoustique de bruit perturbateur a bande(s) etroite(s) a microphone(s) mobile(s), systeme correspondant
WO2014108611A1 (fr) * 2012-12-19 2014-07-17 Ixblue Procédé de contrôle actif acoustique de bruit perturbateur à bandes(s) étroite(s) à microphone(s) mobile(s), système correspondant

Also Published As

Publication number Publication date
AU6824894A (en) 1995-01-03

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