WO1994009484A1 - Active acoustic transmission loss box - Google Patents
Active acoustic transmission loss box Download PDFInfo
- Publication number
- WO1994009484A1 WO1994009484A1 PCT/US1992/008401 US9208401W WO9409484A1 WO 1994009484 A1 WO1994009484 A1 WO 1994009484A1 US 9208401 W US9208401 W US 9208401W WO 9409484 A1 WO9409484 A1 WO 9409484A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- noise
- error
- active
- actuator
- inputs
- Prior art date
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Classifications
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- 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
- G10K11/17883—General system configurations using both a reference signal and an error signal the reference signal being derived from a machine operating condition, e.g. engine RPM or vehicle speed
-
- 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
- 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
- G10K11/17861—Methods, e.g. algorithms; Devices using additional means for damping sound, e.g. using sound absorbing panels
-
- 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
- G10K2210/102—Two 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
- G10K2210/103—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
- G10K2210/106—Boxes, i.e. active box covering a noise source; Enclosures
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- 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
- G10K2210/119—Radiation control, e.g. control of sound radiated by vibrating structures
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- 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
- G10K2210/127—Underwater acoustics, e.g. for submarine
-
- 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
- G10K2210/129—Vibration, e.g. instead of, or in addition to, acoustic noise
-
- 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
- G10K2210/3026—Feedback
-
- 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
- G10K2210/3216—Cancellation means disposed in the vicinity of the source
-
- 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
- G10K2210/3224—Passive absorbers
-
- 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
- G10K2210/3229—Transducers
- G10K2210/32291—Plates or thin films, e.g. PVDF
Definitions
- the present invention relates generally to noise or sound control and more particularly to the control of radiated sound from vibrating machinery by enclosing the machinery in what is termed an "active box or container".
- the purpose of the active box is to markedly reduce the radiation of the sound from the machine to observation points in the surrounding field, with a very lightweight, compact, non-airtight structure.
- the airtight condition implies that it would be extremely difficult to build an effective high TL container for applications which require air flow (e.g. a.c. units, compressors, etc.) or piping and wiring connections or ventilation for cooling. These requirements would imply significant holes through which the acoustic energy could leak.
- air flow e.g. a.c. units, compressors, etc.
- piping and wiring connections or ventilation for cooling e.g. a.c. units, compressors, etc.
- control inputs can be in the form of point force shakers or surface strain devices, such as piezoelectric elements, bonded to the surface of the structure.
- variable to be minimized has to be the radiated sound from the panel, measured, for example, by error microphones located in the radiated sound field as in Fuller.
- the controller format can be any control approach which adjusts the oscillating voltage inputs to the piezoelectric inputs, for example, in order to minimize the radiated sound observed at the error microphones.
- PVDF Polyvinylidene fluoride
- Clark and Fuller demonstrates attenuations of the order of 20 dB of sound radiated from panels in the low frequencies (f ⁇ 600 Hz) with only one or two active actuator inputs.
- Figure 1 is a schematic of a typical box (in this case rectangular) surrounding a noisy machine. The active inputs, error microphones and PVDF film as discussed above are shown. Also demonstrated is an air gap in the box sidewall.
- Figure 2 is a typical general controller arrangement used to derive the correct active control signal, using microphones as error sensors.
- Figure 3 is a typical general controller arrangement used to derive the correct active control signal using PVDF film as an error sensor.
- Figure 4 is a schematic of the use of panels to surround a noisy structure.
- Figure 5 is an azimuth plot of typical noise radiation from an enclosure with and without active control.
- Figure 6 shows a typical noise spectrum at a selected error microphone with and without control. This result shows control of broadband or multiple frequencies simultaneously. Summary of the invention
- the machine to be quieted is surrounded by an active enclosure.
- Arrays of vibration inputs for example, shakers, piezoceramic, etc.
- An array of error microphones are located in the radiated acoustic field or PVDF strips are positioned on the wall.
- a controller senses the levels of sound observed at the error microphones or PVDF film and adjusts the oscillating inputs (in terms of frequency, content, phase and magnitude) to the active vibration inputs in order to minimize the radiated sound.
- the radiated sound from the machine is globally attenuated.
- the container can be of any shape and material, and can have significant air gaps through the walls.
- Transmission Loss Box is shown in Figure 1 as 10.
- a machine 11 is operating and radiating unwanted noise inside the box.
- the machine requires some air flow for cooling etc. as well as piping and electrical connections and an air gap 23 can be provided.
- the machine is surrounded by an enclosure, in this case a rectangular box 12.
- the box 12 is resting on the machine support base 13 but also could totally surround it Damping or absorptive materials can also be added to the box to attenuate high frequency noise and improve the structural response of the enclosure.
- the box can be constructed from a variety of materials such as thin steel, aluminum, etc. In the case shown the box is manufactured from 6.35 mm plexiglass and has dimensions 304.8 x 304.8 x 406.4 mm.
- Piezoceramic control actuators such as 13, 14, 15 (type G1195 of thickness 0.19 mm and dimensions 38.1 x 63.5 mm) are bonded to the center of each panel.
- Each actuator consists of a piezoceramic element bonded onto each side, co-located and wired in parallel with 180° phase shift Such a configuration produces high vibration of the panels.
- These elements can be positioned in various arrays and also embedded in the material if required.
- a number of error microphones such as 16, 17, 18 are positioned in the radiated noise field.
- the number and location of the error microphones is dependent upon the modal contribution (from the panel vibration) and radiation directivity of the noise.
- a controller 19 is employed which measures the output of the error microphones and then constructs an oscillating control signal of the correct frequency content and phase which, when fed to the control actuators 13, 14, 15, etc. causes the sound to be markedly reduced at the error microphones and other locations.
- An alternative to microphones is PVDF thin film which can be placed on the walls in such a way that energy in the radiating modes is sensed.
- One possible configuration for the PVDF strips such as 20, 21, 22 is shown in Figure 1.
- One particular control arrangement embodies the Filtered-X adaptive LMS algorithm discussed by Fuller.
- An oscillating reference signal which has the frequency content of the noise to be canceled is taken from machine 50.
- This reference signal 51 is also highly coherent with the output of the error microphones.
- the reference signal is passed through an analog to digital (A D) converter 52 and fed through a number of adaptive filters 53.
- the number of adaptive filters is equal to the number of control actuators used.
- the arrangement of the adaptive filter is dependent upon the frequency content of the noise.
- the outputs of the adaptive filters is then passed through D/A converters 54 and smoothing filters 55.
- this control signal is typically passed through a high voltage power amplifier and then connected to the electrodes of each actuator.
- the error signals from the microphones 56 are sampled using A D converters and then used in conjunction with the reference signal and a filtered-X update equation in the controller 61 in order to adapt or change the coefficients of the adaptive filters so as to minimize the error signals from the microphones as far as possible.
- the noisy machine is replaced with a 165.1 mm speaker 58 positioned in a 184.2 m x 184.2 m x 114.3 m reflex box.
- Various test frequencies are then fed to the speaker to generate noise.
- the reference signal 51a in this case is taken directly from the signal 59 driving the speaker.
- Figure 5 shows a typical radiation directivity pattern measured around the box at mid plane and a distance of 1.7m.
- the curve 90 labeled “control off” gives the radiated noise field without any enclosure.
- the curve 91 "control on” gives the radiated noise field when the box is in place but the control is not activated. It is apparent that the box only provides a small attenuation of the sound.
- the results of Figure 6, labeled "with control” show high sound reductions of the order of 20 dB at all angles (i.e. global control).
- the active attenuation is achieved as follows.
- the noise source inside the box radiates sound which strikes the enclosure walls and causes it to vibrate (at the same frequency content as the noise source).
- the vibrating walls then radiate sound away to the exterior free field of the box where it appears as unwanted noise.
- the active inputs work as follows.
- the structural actuators cause anti-vibration in the walls of the enclosure. When the inputs to the structural actuators are adjusted correctly these anti-vibrations cancel out those vibrations in the box which were previously radiating sound, thus leading to global sound reduction.
- not all vibrations (or modes) in the enclosure will radiate sound and thus the active inputs need only cancel those vibrations (or modes) that are efficient radiators rather than controlling _aU the vibration. This approach leads to a very low number of control actuators as opposed to totally canceling the box vibration, and is the key to the success of the approach.
- An alternative, shown in Figure 4, is to enclose the noisy structure 80 with close fitting panels 85 instead of a free standing enclosure.
- the enclosure panels are attached directly to the sides of the noise source. If the regions generating noise are localized or if noise control is needed in certain directions, an advantage to this method is that the need to enclose the entire structure is eliminated. In addition, in many cases a more compact enclosure can be constructed without restricting airflow needed for cooling.
- An example of an application of this method would be for the reduction of "hum" from electrical transformers. Transformer noise is generated from magnetostrictive forces in the coil and are propagated to the transformer skin through the oil field and coil foundation.
- Figure 4 shows a cancellation system 80 for enclosing a noisy structure with close fitting panels.
- Controller 81 receives a reference signal 82 from the structure and inputs 83, from error microphone 84.
- Actuators 86 are located on close fitting panels 85.
- Still another alternative shown in Figure 3 is to place the actuator directly on the surface of the noise source.
- Figure 3 shows noise reduction system 70 with active structural control provided with a Noise Cancellation Technologies, Inc. controller 71 and power amplifier 72 having outputs to piezoceramic actuators such as 73, 74 and inputs from PVDF sensor film strips such as 75, 76, 77.
- controller 71 and power amplifier 72 having outputs to piezoceramic actuators such as 73, 74 and inputs from PVDF sensor film strips such as 75, 76, 77.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1992/008401 WO1994009484A1 (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
CA002145862A CA2145862C (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
US08/411,779 US5692053A (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
DE69230007T DE69230007T2 (en) | 1992-10-08 | 1992-10-08 | Housing with actively generated acoustic transmission loss |
EP93904473A EP0664044B1 (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
PCT/US1992/008401 WO1994009484A1 (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
CA002145862A CA2145862C (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1994009484A1 true WO1994009484A1 (en) | 1994-04-28 |
Family
ID=25677870
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1992/008401 WO1994009484A1 (en) | 1992-10-08 | 1992-10-08 | Active acoustic transmission loss box |
Country Status (2)
Country | Link |
---|---|
CA (1) | CA2145862C (en) |
WO (1) | WO1994009484A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2740600A1 (en) * | 1995-10-27 | 1997-04-30 | Metravib Sa | Active noise reduction method for vibrating electrical machinery |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2776020A (en) * | 1955-02-09 | 1957-01-01 | Gen Electric | Noise reducing system for transformers |
US3602331A (en) * | 1969-04-12 | 1971-08-31 | Messerschmitt Boelkow Blohm | Sound shielding by means of sound |
US4025724A (en) * | 1975-08-12 | 1977-05-24 | Westinghouse Electric Corporation | Noise cancellation apparatus |
US4689821A (en) * | 1985-09-23 | 1987-08-25 | Lockheed Corporation | Active noise control system |
US5091953A (en) * | 1990-02-13 | 1992-02-25 | University Of Maryland At College Park | Repetitive phenomena cancellation arrangement with multiple sensors and actuators |
-
1992
- 1992-10-08 WO PCT/US1992/008401 patent/WO1994009484A1/en active IP Right Grant
- 1992-10-08 CA CA002145862A patent/CA2145862C/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2776020A (en) * | 1955-02-09 | 1957-01-01 | Gen Electric | Noise reducing system for transformers |
US3602331A (en) * | 1969-04-12 | 1971-08-31 | Messerschmitt Boelkow Blohm | Sound shielding by means of sound |
US4025724A (en) * | 1975-08-12 | 1977-05-24 | Westinghouse Electric Corporation | Noise cancellation apparatus |
US4689821A (en) * | 1985-09-23 | 1987-08-25 | Lockheed Corporation | Active noise control system |
US5091953A (en) * | 1990-02-13 | 1992-02-25 | University Of Maryland At College Park | Repetitive phenomena cancellation arrangement with multiple sensors and actuators |
Non-Patent Citations (2)
Title |
---|
IBM Technical Disclosure Bulletin, Volume 31, No. 8, January 1989, "Audible Noise Suppression", see page 256, third paragraph, and page 257, third paragraph. * |
See also references of EP0664044A4 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2740600A1 (en) * | 1995-10-27 | 1997-04-30 | Metravib Sa | Active noise reduction method for vibrating electrical machinery |
Also Published As
Publication number | Publication date |
---|---|
CA2145862C (en) | 1999-03-09 |
CA2145862A1 (en) | 1994-04-28 |
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