Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N1/00—Silencing apparatus characterised by method of silencing
  • F01N1/02—Silencing apparatus characterised by method of silencing by using resonance
  • F01N1/023—Helmholtz resonators
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N1/00—Silencing apparatus characterised by method of silencing
  • F01N1/06—Silencing apparatus characterised by method of silencing by using interference effect
  • F01N1/065—Silencing apparatus characterised by method of silencing by using interference effect by using an active noise source, e.g. speakers
• • 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
  • G10K11/17855—Methods, e.g. algorithms; Devices for improving speed or power requirements
• • 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
  • 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
  • G10K11/17875—General system configurations using an error signal without a reference signal, e.g. pure 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
  • G10K2210/10—Applications
  • G10K2210/105—Appliances, e.g. washing machines or dishwashers
  • G10K2210/1053—Hi-fi, i.e. anything involving music, radios or loudspeakers
• • 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
  • G10K2210/111—Directivity control or beam pattern
• • 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
  • G10K2210/112—Ducts
• • 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
  • G10K2210/1282—Automobiles
  • G10K2210/12822—Exhaust pipes or mufflers
• • 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
  • G10K2210/321—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
  • G10K2210/3219—Geometry of the configuration
• • 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
  • G10K2210/3227—Resonators
  • G10K2210/32272—Helmholtz resonators

Definitions

• PCT ⁇ JS91/02731 "Improvements In and Relating to Transmission Line Loudspeakers" to Hoge et al.
• the descriptions below utilize the transducers described by the above mentioned documents.
• the current invention seeks to add enhancements which improve the packagability and durability of these active muffler devices.
• the importance of durability and low cost in such systems can not be overstated.
• Passive devices which represent the current state of the art are inexpensive and very durable, sometimes performing for decades without attention of any kind. Therefore, it is essential to utilize the lowest cost, most durable system to enhance the operation of active systems.
• the invention relates to the enhancement of active acoustical attenuation by coupling an engine exhaust pipe with the acoustic exhaust of an active enclosure.
• a secondary source When active noise control is applied to an offending noise source, a secondary source is placed in close proximity to the offensive noise source.
• the secondary source can be placed either around the offensive noise source, concentrically, or beside the noise source, in a dipole configuration, as long as the separation between the two source centers is much smaller than the wavelength of the highest frequency of cancellation.
• the secondary source creates an acoustic waveform equal in amplitude and 180 degrees out of phase from the offensive source.
• the secondary source is driven by an adaptive controller system that requires a feedback microphone. The feedback microphone measures the effectiveness of the destructive interference and is used to adjust the signal of the secondary source and optimize cancellation.
• the port extension is fitted over the end of both the engine exhaust pipe and the acoustic port.
• the port extension allows for better coupling between the exhaust noise and the anti-noise emitted from the active enclosure acoustic port.
• the results of this improved coupling is increased acoustical attenuation using less electrical power.
• the port extension also channels the harmful exhaust fumes and allows the fumes to exit out from underneath the car at the regulatory distance. This feature allows the active enclosure to be positioned further underneath the car, from the bumper and from the road surface.
• both the engine exhaust pipe and the acoustic port can be much shorter. Shortening the acoustic port reduces the acoustic mass of the port which increases the acoustic output of the active enclosure. An increase in output power is always desirable.
• the instant invention further contemplates the use of a duct extension into which both the anti-noise and exhaust pipe noise enter, are mixed and conformed to a plane wave and a sensing microphone samples the resulting plane wave noise to cause adjustments to be made, if needed, to the control means.
• the duct extension is connected via a port, usually the same size or larger than the exhaust pipe, to an enclosure containing the active noise cancelling speaker with accompanying front and back cavities.
• a port connecting the cavities may be provided.
• the dimensions and relationship between the cavities and the speaker are generally dictated by the theory and desired response curves as discussed by A. N. Thiele, "Loudspeakers in Vented Boxes; Part 1", Journal of the Audio Engineering Society. March 1961, pages 181-191 and "Closed-Box Loudspeaker Systems Part II: Synthesis", Journal of the Audio Engineering Society. Pages 282-289, by Richard H. Small.
• the size of the duct extension must be such that its cross-sectional area is large enough so that the cut-on frequency of non-plane wave (or higher order) is above the operating frequency of the active noise controller. Once this criteria is established and met the actual shape of the duct extension is not that important even though it determines what the cut-on frequency will be.
• the end of the duct extension can be beveled or styled in any number of ways to conform to, e.g., an automotive style.
• the length of the duct extension is preferably greater and from two to three times its reduced circular cross-section diameter.
• the extension changes the dipole radiation into a plane wave which is then sensed by a residual microphone which inputs to the controller how well the device is working and causes it to rapidly adapt to achieve full attenuation.
• the diameter of the port connecting the enclosure with the duct extension should be at a minimum as large as the exhaust pipe diameter and should be relatively short to reduce acoustic mass.
• the control system for the invention may use the sync control described in U.S. Patent No. 4,490,841 to Chaplin, the control described in U.S. Patent No. 5,105,377 to Ziegler or that described in co-pending PCT application Serial No. PCT/US92/05228, entitled "Control System Using Harmonic Filters”. All these control systems use a residual microphone and a sync to an engine or motor.
• the control system also may use the digital virtual earth/adaptive feedforward system described in co-pending U.S. Patent application, Serial No. 08/188,869, entitled "Adaptive Feedforward and Feedback
• the invention provides improved coupling between a dipole oriented engine exhaust and an active enclosure acoustic port. It increases the amount of attenuation achievable with a dipole oriented engine exhaust and an active enclosure acoustic port and decreases the amount of power required to achieve a certain amount of attenuation for a given active noise cancellation system.
• the arrangement provides protection to the error sensor from road debris, provides a way to integrate the error sensor cable into the active enclosure to minimize cables and protects the cable by encasing it in a conduit.
• the arrangement has a flared port to reduce turbulence and an internal heat shield to protect the error sensor or sensing microphone.
• the duct extension can be styled in a variety of shapes.
• Another object of this invention is to increase the amount of attenuation achievable with a dipole oriented engine exhaust and active enclosure acoustic port.
• a further object of this invention is to decrease the amount of power required to achieve a certain amount of attenuation for a given active noise cancellation system in a dipole orientation.
• a still further object of this invention is to allow the active enclosure to be mounted further behind the automobile muffler and further from the road surface. Yet another object of this invention is to provide a channel which will allow harmful engine exhaust gases to exit out from underneath the vehicle at the regulatory distance.
• Additional objects of the invention include:
• Figure 1 is a plan view of one embodiment of this invention
• Figure 2 is a perspective view of the embodiment of Figure 1
• Figure 3 is a diagrammatic view of the speaker enclosure
• Figure 4 is an end view of the speaker enclosure of Figure 3 showing its relationship to a tailpipe
• Figure 5 shows an alternative embodiment of the speaker enclosure
• Figure 6 is a perspective view of a third embodiment of the invention.
• Figure 7 is a cross-sectional view of the port connection of Figure 6,
• Figure 8 is a cross-sectional view of the speaker enclosure of Figure 6,
• Figure 9 is a block diagram of the control system
• Figure 10 is a partial perspective view of a heat shield/air vent/cable conduit.
• the proposed invention utilizes basic configurations similar to those described by Ziegler et al and Hoge et al in the above mentioned patent and patent application.
• the instant device instead of being arranged concentric with the pipe is non- integral with the pipe as shown in Figure 1.
• Anti-source, 2 is placed such that the outlet, 3, is placed near the outlet of pipe, 1, connected to passive muffler, 15, which contains a flow of gas containing pressure pulsations.
• Passive muffler, 15, is used to reduce noise at frequencies above the capability of the active anti-source.
• Active transducer means, 2 consists of outlet acoustic mass, 4, acoustic compliances 5 and 6, speaker driver, 7, and, optionally, an acoustic mass, 8.
• Figure 2 shows a variation.
• Figure 2a shows the two outlets from the end. If a microphone, 9, is placed on the plane, 10, between the pipe, 1, outlet and the active source outlet, 3, the electronic controller will cause the two sources to form an acoustic dipole.
• a dipole has a directional radiation pattern, but if the acoustic centers of the two sources are within approximately one tenth of a wavelength the minimum cancellation will be approximately 10 decibels. This minimum will occur along the line through the centers of the source and anti-source. For this reason, it is sometimes advantageous to orient the two sources above and below each other, as shown in Figure 2, since microphones or listeners are less likely to be located above or below the sources if the device is mounted on a vehicle.
• the active source can be located remotely from the hot exhaust pipe. This increases the potential that packaging solutions can be found, particularly on automobiles, in which the space limitations are severe. More importantly, though, the remote location of the active source allows different materials to be used in the construction of the active source to save weight, reduce cost and improve durability. For example, whereas the challenges of using plastic to construct the anti-noise source were severe when the source was in direct contact with the exhaust pipe, the use of plastic is a simple matter with the new outlet arrangement.
• the active source now can be disguised as a traditional "dual" exhaust package, . which reduces the.possibility consumers will react negatively to its appearance.
• the non- integral active muffler can now be placed within the vehicle's trunk if necessary and its use in what were near-impossible applications is now easier.
• marine mufflers in which a flow of water is mixed with the hot gases are now possible without exposing the active transducer to water.
• the transducer can be mounted above the waterline.
• Figure 3 One alternative arrangement is shown in Figure 3 in which the non-integral active muffler outlet is pointed 90 degrees away from the pipe outlet. In this manner, the acoustic centers of the two noise sources can be moved closer together to extend the upper frequency limit of the system.
• Figure 6 shows the perspective of a third preferred embodiment of the invention.
• the apparatus generally denoted as 40 has a speaker enclosure 41 with a connecting port 42 to duct extension 43.
• An opening in extension 43 is adapted to receive the end of tail or exhaust pipe 44 and be secured thereto by an annular clamping means 45 which is similar to a pipe clamp.
• Port 42 and pipe 44 enter duct extension 43 side by side so as to create dipole radiation of noise.
• Duct 43 alters and compresses this radiation into a plane wave which is sensed by microphone 46 as it exits the open end 47 of duct extension 43.
• Tailpipe 44 is connected via clamp 48 to straight through muffler 49.
• the diameter of port 42 is at least as large as the diameter of tailpipe 44.
• the cross-sectional area of duct extension 43 is such that the cut-on frequency of non-plane wave behavior or propagation is above the operating frequency of the controller and its length 1 is 2 to 3 times its reduced circular cross section.
• Dimension "a” should be as short as possible to reduce acoustic mass.
• Figure 7 shows the inside of port 42 to be flared as at 50 to reduce flow turbulence.
• Figure 8 shows a cross-sectional view of speaker enclosure 41 with rear cavity 51, front cavity 52 and speaker 53. If required, a second speaker 54 may be added. A port 55 may also be provided to make the arrangement behave as a 6th order speaker as described in PCT/US91/02731 and herein incorporated by reference.
• control system is shown generally in Figure 9 with controller 60 and amplifier 61 driving speaker 53 in enclosure 41.
• Power supply 62 is connected to controller 60 as is residual microphone 46. If the system is using only a residual microphone a sync connection 63 to an engine flywheel 64 or the like is necessary. If no sync is used a digital virtual earth or an adaptive feedforward system with an upstream sensing microphone 65 can be used.
• Figure 10 shows a combination hollow heat shield and conduit unit 70 mounted atop duct 43 and containing a cable 71 to microphone 46, enclosed by 70 which also has vent holes 72, 73 to allow air to ingress and egress to cool microphone 46.
• the unit also protects microphone 46 from road debris and the like.
• the conduit unit 70 is actually ' mounted on heat shield 74 which is held in a spaced relationship to duct 43 by spacers 75. This allows for further heat relief of microphone 46.
• Conduit 70 has two passageways, one for the cooling air and one for the cable 71.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Acoustics & Sound (AREA)
• Multimedia (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Exhaust Silencers (AREA)
• Soundproofing, Sound Blocking, And Sound Damping (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=22906491

Family Applications (1)

Country Status (4)

Cited By (5)

Families Citing this family (2)

Citations (2)

Family Cites Families (3)

• 1995
  • 1995-05-09 EP EP95918421A patent/EP0828466A1/en not_active Withdrawn
  • 1995-05-09 JP JP52915795A patent/JP3290991B2/ja not_active Expired - Fee Related
  • 1995-05-09 CA CA002188534A patent/CA2188534C/en not_active Expired - Fee Related
  • 1995-05-09 WO PCT/US1995/005721 patent/WO1995030393A1/en not_active Application Discontinuation

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events