1. Active Noise Control - Wikipedia, The Free Encyclopedia Active noise control (ANC) (also known as noise cancellation, active noise reduction (ANR) or antinoise) is a method for reducing unwanted sound. http://en.wikipedia.org/wiki/Active_noise_control

Active noise control From Wikipedia, the free encyclopedia Jump to: navigation search Active noise control (ANC) (also known as noise cancellation active noise reduction (ANR) or antinoise ) is a method for reducing unwanted sound Contents Explanation Applications See also References ... edit Explanation Sound is a pressure wave , which consists of a compression phase and a rarefaction phase. A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase ) to the original sound. The waves combine to form a new wave, in a process called interference , and effectively cancel each other out - an effect which is called phase cancellation . Depending on the circumstances and the method used, the resulting soundwave may be so faint as to be inaudible to human ears. A noise-cancellation speaker may be co-located with the sound source to be attenuated . In this case it must have the same audio power level as the source of the unwanted sound. Alternatively, the transducer emitting the cancellation signal may be located at the location where sound attenuation is wanted (e.g. the user's ear). This requires a much lower power level for cancellation but is effective only for a single user. Noise cancellation at other locations is more difficult as the three dimensional wavefronts of the unwanted sound and the cancellation signal could match and create alternating zones of constructive and destructive interference. In small enclosed spaces (e.g. the passenger compartment of a car) such global cancellation can be achieved via multiple speakers and feedback microphones, and measurement of the modal responses of the enclosure.

2. Active Noise Control | Ask.com Encyclopedia Active noise control (ANC) (also known as noise cancellation, active noise reduction (ANR) or antinoise) is a method for reducing unwanted sound. http://www.ask.com/wiki/Active_noise_control?qsrc=3044

3. Active Noise Control | TripAtlas.com Active noise control (ANC) (also known as noise cancellation, active noise reduction (ANR) or antinoise) is a method for reducing unwanted sound. http://tripatlas.com/Active_noise_control

4. Active Noise Control - SFGate Topics Active noise control Topic on SFGate.com News and archives about Active noise control, Active noise control Media Photos and Video http://topics.sfgate.com/topics/Active_noise_control

5. NVHmaterials.com - Links Database Welcome to the Best Web Page for complete links to information and websites around the world for materials that affect Noise, Vibration, and Harshness (NVH) performance http://www.nvhmaterials.com/nvh/Active_Noise_Control/index.htm

home about us search tips contact ... email Check out the new NVHmaterials.com discussion board and forums The site has recently undergone a complete overhaul. Please contact Paul Sakion with any comments or changes NVHmaterials.com NVHmaterials.com links database is a free service supported by advertising. If you find the site useful, please take a moment to click on one of our sponsor's links below. Many links contain a wealth of additional information on NVH materials and testing! Top : Active Noise Control NVHmaterials.com - Links Database: Active Noise Control Home Add a Resource Modify a Resource What's New ... Search Links: Active Noise Control FAQ - FAQ's, references, and links to other sites involved with active noise control pop (Added: 11-Jun-2000 Hits: 1463 Rating: 9.33 Votes: 3) Rate It Noise Control - A noise control manufacturers directory including soundproofing, sound barriers, soundproofing material, active noise control, sound proof enclosure, soundproof wall, acoustical foam, acoustical wall panels, industrial noise control, sound absorbers, noise barriers, sound reduction, sound enclosures, and noise barrier. pop (Added: 26-Jan-2004 Hits: 732 Rating: Votes: 0) Rate It Signal Systems Corporation - We specialize in signal processing, noise reduction and active noise control

6. Active Noise Control - On Opentopia, Find Out More About Active Noise Control Active noise control (also known as noise cancellation, active noise reduction (ANR) or antinoise) is a method for preventing unwanted sound. http://encycl.opentopia.com/term/Active_noise_control

About Opentopia Opentopia Directory Encyclopedia ... Tools Active noise control Encyclopedia A AC ACT : Active noise control Active noise control (also known as noise cancellation active noise reduction (ANR) or antinoise ) is a method for preventing unwanted sound Contents 1 Explanation 2 Applications 3 See also 4 External links Explanation Sound consists of vibration s in the air , which can be represented as a wave . If a speaker emits a sound whose wave has the same amplitude and the opposite polarity to the original sound, the waves cancel out and the result is no sound at all. A computer analyzes the waveform of the background aural or nonaural noise, then generates a polarity reversed waveform to cancel it out by interference . It does not mean that all frequencies are rotated 180° out of phase (phase shifting). This waveform has identical or directly proportional amplitude to the waveform of the noise, but its polarity (not the phase) is the opposite. This creates destructive interference that reduces the amplitude of the perceived noise. This method differs from passive noise control methods ( soundproofing ) in that a powered system is involved, rather than unpowered methods such as insulation, sound-absorbing ceiling tiles, or automobile

7. Active Noise Control Research results and software tools for using smart materials in active noise control. Active noise control and noise cancellation solutions for acoustic problems brought to you by Signal Systems Corporation. http://www.signalsystemscorp.com/ancindex.htm

Home Projects Contact Personnel ... ANC Status Active Noise Control Active Noise Control quiets offensive noise by using cancellation techniques, or anti-sound. Signal Systems Corporation's mission is to help quiet irritating noises so you can have a more peaceful life. This web site is designed to give the active noise community a common source for information about this technology, its applications and suppliers. Please use the feedback link at the bottom of each page to let us know how we can improve this site. Active Noise Control Headphones What is active noise control? Check out the ANC FAQ Where is active noise control technology going ? Read our discussion about commercializing ANC technology

8. Campanella Associates (Acoustics Consultants) - Active Noise Control Campanella Associates is dedicated to making the home, work, institutional and recreational environments pleasant and safe. As acoustical engineers, we provide our clients with http://www.campanellaacoustics.com/anc.htm

Active Noise Control or Cancellation (ANC) Many folks have called us to ask about the easibility of ANC in reducing domestic and commercial noise problems. The conventional wisdom seems to be that most noise situations are amenable to an ANC solution. This is false, just as is the notion that the computer is the solution to all calculation and bookkeeping problems, or that computers reduce the consumption of paper. Consider that most general noise problems are 3-dimensional in nature, typically a noisy area where one or more persons work or relax. Some explanation is in order: ANC uses the principle of destructive interference, where the noise sound wave is sensed with a microphone. This signal is amplified and fed to a loudspeaker which emits sound of the same type but of opposite phase with respect to the original sound wave. Such cancellation can occur at only one lpoint in space. In the case of one-dimensional propagation down a duct, the sound wave for all intents is "stopped" at that point since the sound from the loudspeaker proceeds one - dimensionally down the duct, matching the original noise waves precisely along the way. (upstream toward the sound source, the sound wave is doubled, but that is of no concern. In the case of two or three dimensional propagation into space as into a room, The spreading of the loudspeaker sound does not match the pattern of the divergence of the noise field, having

9. Active Noise Control FAQ Provides answers to common questions about active noise control including a discussion of popular misconceptions about what active noise control can and cannot do. http://www.chrisruckman.com/ancfaq.htm

visitors since 2/4/2007. Active Noise Control FAQ The "FAQ" you are now reading discusses active noise control, a way of using basic physics to control noise and/or vibration. What is an FAQ, you say? It's a "Frequently Asked Questions list." The Internet supports thousands of "newsgroups" - discussion forums covering every imaginable topic. When certain questions tend to get asked over and over again, it's common to assemble the answers into a list for easy reference. This particular FAQ was written for the newsgroups news:alt.sci.physics.acoustics and news:comp.dsp to serve four purposes: Provide concise, accurate answers to common questions about active noise control. Dispel popular misconceptions about what active noise control can and cannot do. Refer readers to web links, technical references, and other sources of information. Stimulate public interest in acoustics. Use the links at left, or click here to download the entire FAQ as a single text file.

10. Industrial Acoustics Company (IAC) - Leading Supplier Of Noise And Acoustic Cont Suppliers of noise and acoustic barriers, panels, doors, structures and test facilities. http://www.industrialacoustics.com/uk/

Group Home UK home UK Office International Office ... Key People Noise and acoustic control products, structures, test facilities and aero-engine testing solutions From its Global Headquarters in Winchester UK, IAC, a world leader, offers imaginative solutions to an extraordinarily wide range of noise pollution and sound quality problems. Market leaders since 1949 100% products acoustically-rated A Quality Management system in accordance with ISO 9001: 2008 BS EN ISO 14001 environment management registered Over 1000 employees, representatives and licensees worldwide Industrial Acoustics Company supplies a large and diverse noise control product range to over 50 countries throughout the Americas, Europe, Africa, the Middle East and Pacific Rim. We supply 9 market sectors worldwide: Manufacturing and Process Industries Our Silencers and Acoustic Enclosures provide noise reduction for manufacturing/process industries while our rugged Noise Barriers reduce noise pollution from factories, roads and railways.

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12. Vibrations & Acoustics Laboratories | Vibration & Acoustics Laboratories Research at Virginia Tech. http://www.val.me.vt.edu/

Leaders in Research and Technology in Sound and Vibration Aircraft landing gear model for wind-tunnel noise testing Cessna 150 aircraft fuselage for noise treatment testing Commercial autonomous underwater vehicle Instrumented mannequin for characterizing headsets Setting up array measurement in anechoic chamber Instrumenting aircraft fuselage interior Students working on autonomous ATV project Autonomous ATV automatic braking linkage Underwater instrumentation testing Acoustic array instrumentation setup Virginia Tech Home College of Engineering VAL Home Page About VAL Mission Statement Contact VAL Directions to VAL VAL Team Fun People Core Faculty VAL Personnel Graduate Students Research Topics Resources Active Noise Control Demo Publications Resources Facilities Equipment Computing Resources Opportunities ... Related Links Latest VAL News Three VAL students received high honors at the North Carolina Acoustical Society of America [NC-ASA] chapter meeting in March 2010. Read More... Professor Ricardo Buridisso completes his experimental testing to help validate modelling of sonic boom propagation in buildings. The video of the sonic boom simulation can be found here Read More...

13. Active Noise Control Equipment On ThomasNet.com Welcome to the premier industrial Noise Control Equipment Active resource. A wide variety of manufacturers, distributors and service companies are featured in our extensive http://www.thomasnet.com/products/noise-control-equipment-active-53824801-1.html

14. Applied Acoustics - Active Noise Control When quarter 5. Course code VTA130. Credits 7.5 ECTS. Exam written and/or oral. Contact Wolfgang Kropp. Course Page http://www.ta.chalmers.se/education.php?page=crs_anc

15. Noise Control And Sound Control Products, Sound Proofing, Noise Enclosures And A Supplier of noise and sound control products for industry. Provides details of products and applications. http://www.enoisecontrol.com

Home Contact Us Order Info Clients ... Related Videos Applications Menu Acoustical Consultant Industrial Noise Control HVAC Noise Control Noise Ordinance Products Menu Sound Curtains Sound Enclosures Sound Barrier Wall Outdoor Sound Curtains ... Soundproof Case Studies Chiller Noise Hydraulic Pump Noise Air Compressor Noise Quiet Room ... Acoustic Blankets - Chillers and Compressor Noise Unger Technologies, Inc. is your trusted source for noise control solutions. We are a nationwide company dedicated to the field of noise control products and services including: Engineered sound control products Acoustic consulting and design Our engineered products, capabilities, knowledge and expertise make us an ideal partner for your noise control project. Call our company today to further discuss your particular noise application. Call Today at 888.213.4711 Email Us (info@enoisecontrol.com) Fax Us at 317.774.1911 Ask a Question Sound Curtains HVAC Noise Control Outdoor Sound Curtain ... Sound Enclosure Typical Applications (click to view) Air Compressor PD Blower Transfer Pump Punch Press ... Gym, Church, Multi-Purpose Room

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17. Active Noise Control System With A Helmholtz Resonator - Patent EP1313090 An active noise control system (26) includes an error microphone (28), a speaker (29) and an active resonator (30) which communicate with an ANC controller (32). The active http://www.freepatentsonline.com/EP1313090.html

18. Envirotech Systems Pvt. Ltd. Manufacturer of sound testing chambers and acoustic enclosures. http://www.envirotechsystems.tradeindia.com

Home Page Company Profile Our Products Acoustic Enclosures for DG Sets ... Acoustic Ceiling Tiles About Us With an objective to provide high quality range of products at highly competitive prices, Envirotech Systems Pvt. Ltd. started its operations in the year 1997. We, as a professionally managed organization, have achieved specialization in designing and developing wide range of acoustic enclosures for various applications. With our consistent effort and continuous dedication towards quality and customers satisfaction, we have become a reliable manufacturer in Acoustics like Acoustic Enclosures, Room Acoustic, Sound Testing Chamber, Anechoic Chambers, Diesel Generator Room Acoustic, Acoustic Louvers, Acoustic Barriers, Sound Proof Curtains, Noise Testing Booth, RF Shielded Enclosures/ Rooms, Studio Acoustic and many more. Engineering excellence and stringent quality control norms at each stage of production, we ensure optimal performance of our range. We provide excellent after sales services across the country and maintain a huge inventory of spare parts to meet immediate bulk requirements of the same. We also arrange training program for your operational team. Our Products As one of the most preferred manufacturer of the industry, we Envirotech Systems Pvt. Ltd. offer following range of products:

19. Active Noise Control Demo | Vibration & Acoustics Laboratories With this shareware, you can test and experiment with a very simple active noise control system at home. The purpose of this experiment is to demonstrate active noise control. http://www.val.me.vt.edu/research/activenoisecontrol

Home Active Noise Control Demo With this shareware, you can test and experiment with a very simple active noise control system at home. The purpose of this experiment is to demonstrate active noise control. The basic principle of active noise control is to cancel a sound wave (noise) by emitting a secondary opposite (out-of-phase) sound wave (control wave). The active noise control principle is illustrated in the figure below. In the real world, the implementation of active noise control is much more complex due to phase and spatial matching, efficient transducers, system identification, etc., as explained in the paper "Active Control of Sound and Vibration," by C. R. Fuller and A. H. Flotow. The shareware that you can download, sends a single frequency wave (sine wave at 1000 Hz) to your right speaker. This sound wave represents the noise to be cancelled. By activating the control (pushing on the control button in the program), sound wave of equal amplitude and opposite phase is sent to the left speaker to cancel the noise. Note that for an effective demonstration, the two speakers should face each other and be close to one another (see picture above). If desired, the speakers can then be moved apart and the resulting effect on the sound cancellation observed. This share was tested using "Labtec LCS-800" speakers; the sound cancellation obtained was large and appreciable. Note that the control results depends highly on the quality of speakers used. Please make sure that the volume of each speaker is set to be identical. Also notice that this experiment is more impressive at medium-high volume (please be careful not to overdrive your speakers and ears!).

20. Active Noise Control - US Patent 4876722 Abstract Patent Abstract An active noise control system for reducing the amount of noise propagated along a duct comprises a microphone mounted in the wall of the duct for detecting http://www.patentstorm.us/patents/4876722.html

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