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NOISE CANCELLATION DoctorD.WebHop.Net

NOISE CANCELLATION http://DoctorD.WebHop.Net. INTRODUCTION TECHNOLOGY APPLICATIONS DEMONSTRATION SUMMARY. NOISE CANCELLATION INTRODUCTION. NOISE REDUCTION TECHNIQUES MECHANICAL DESIGN BALANCE TRANSIENTS RESONANCES PASSIVE ATTENUATION ENERGY ABSORBING MATERIALS COMPLIANT MOUNTS

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NOISE CANCELLATION DoctorD.WebHop.Net

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  1. NOISE CANCELLATIONhttp://DoctorD.WebHop.Net • INTRODUCTION • TECHNOLOGY • APPLICATIONS • DEMONSTRATION • SUMMARY Active Noise Cancellation

  2. NOISE CANCELLATIONINTRODUCTION • NOISE REDUCTION TECHNIQUES • MECHANICAL DESIGN • BALANCE • TRANSIENTS • RESONANCES • PASSIVE ATTENUATION • ENERGY ABSORBING MATERIALS • COMPLIANT MOUNTS • ACTIVE SYSTEMS: NOISE CANCELLATION • APPLICATIONS • STATUS "NOISE CANCELLATION TECHNOLOGY IS APRACTICAL SOLUTION TO REAL WORLD PROBLEMS" Active Noise Cancellation

  3. NOISE CANCELLATIONANTI-NOISE "ACTIVE NOISE CANCELLATION DOES NOT MASK THE NOISE, IT REMOVES A SIGNIFICANT PORTION OF THE NOISE FROM THE ENVIRONMENT" Active Noise Cancellation

  4. NOISECANCELLATIONTECHNOLOGY • NOISE • BROAD BAND • TURBULENT OR RANDOM NOISE • NARROW BAND • TONAL OR HARMONIC NOISE • PASSIVE NOISE CONTROL • LOCALIZE VIBRATION AND ABSORB ENERGY • EFFECTIVE AT HIGH FREQUENCIES • ACTIVE CANCELLATION • TWO BASIC APPROACHESBROAD BAND - ADAPTIVELY FILTER THE SIGNAL FROM AN "UPSTREAM" SENSOR TO CREATE THE ANTI-NOISE SIGNALSYNCHRONOUS - ADAPTIVELY SYNTHESIZE AN ANTI-NOISE SIGNAL WITH A-PRIORI KNOWLEDGE OF THE BASIC "NOISE CYCLE" RATE • EFFECTIVE AT LOW FREQUENCIES "A GOOD SOLUTION USUALLY REQUIRES A COMBINATION OF PASSIVE AND ACTIVE TECHNIQUES" Active Noise Cancellation

  5. NOISE CANCELLATIONEXAMPLE APPLICATIONS • AT SOURCE • MUFFLER • ALONG A TRANSMISSION PATH • IN-DUCT FAN NOISE • COMPLIANT MOUNT • AT THE EAR • HEADSET • Broadband • Selective Narrow Band • QUIET ZONE • Cabin Quieting • IN-WIRE • COMMUNICATIONS "ENGINEERING SOLUTIONS TO NOISE PROBLEMS REQUIRES AS MUCH REAL WORLD APPLICATION KNOWLEDGE AS IT DOES KNOWLEDGE OF ACTIVE NOISE CANCELLATION TECHNOLOGY" Active Noise Cancellation

  6. AT SOURCE: MUFFLER(NARROW BAND NOISE CANCELLATION) IT IS USUALLY BEST TO CANCEL THE NOISE AS CLOSE AS POSSIBLE TO THE SOURCE" Active Noise Cancellation

  7. AT SOURCE: MUFFLER(CONTINUED) • CHARACTERISTICS • STRAIGHT THROUGH PASSIVE MUFFLER REDUCES BACKGROUND AND HIGH FREQUENCY NOISE • ACTIVE CANCELLATION AT THE END OF THE EXHAUST GLOBALLY REDUCES TONAL NOISE COMPONENTS TO THE BACKGROUND • BENEFITS • LOW BACK PRESSURE • FUEL ECONOMY • QUIET • SIZE AND WEIGHT • APPLICATIONS • PRIMARY POWER EXHAUST • AUXILIARY POWER GENERATORS (EXHAUST NOISE) • BULK TRANSFER VACUUM SYSTEMS • COMPRESSOR INLET NOISE Active Noise Cancellation

  8. Vacuum Muffler • Application: 100 horsepower diesel vacuum. Used to load and unload railroad cars (CSX MasterVac –10/1990) • Noise Sources • Vacuum Exhaust: An Active Muffler, along with a straight-through, passive muffler. • Diesel Exhaust: a better passive muffler. • Engine Block: Passive housing. • Vibration: Compliant mounts. Active Noise Cancellation

  9. Vacuum Muffler(Continued) “The quiet system loads/unloads a rail car 20% faster than the noisy system it replaced.” Active Noise Cancellation

  10. CSX MasterVac Active Noise Cancellation

  11. Diesel Engine Muffler • Application: 450 horsepower diesel engine. 522 in3, 2-stroke Used to generate electrical power (Detroit Diesel 6V-92 at 1800 RPM) • Noise Sources • Exhaust: An Active Muffler, along with a straight-through, passive muffler. • Air Intake: Air filter • Engine Block: Passive housing. • Vibration: Compliant mounts. Active Noise Cancellation

  12. Diesel Muffler Results(Demonstration Audio) “The Active muffler system is 20% smaller than the conventional passive muffle it replaced.” Active Noise Cancellation

  13. Along a Transmission Path(Broadband Noise Cancellation) "FEED FORWARD CANCELLATION IS THE CLASSICAL APPROACH AND IS OFTEN HIGHLIGHTED IN THE TECHNICAL LITERATURE" Active Noise Cancellation

  14. CONTROLLING VIBRATION "CONTROLLING VIBRATION NEAR THE SOURCE CAN GREATLY REDUCE ACOUSTICAL NOISE AND REDUCE WEAR" Active Noise Cancellation

  15. COMPLIANT MOUNT(CONTINUED) • CHARACTERISTICS • ROTATING MACHINE FLOATS FREELY AT VIBRATION FREQUENCIES • NO VIBRATION ENERGY IS TRANSMITTED THROUGH THE MOUNT • FAIL SAFE - THE PASSIVE MOUNT IS STILL THERE IF THE ACTIVE SYSTEM STOPS WORKING • BENEFITS • OPERATOR COMFORT - VIBRATIONREDUCED • SECONDARY ACOUSTICAL NOISE ELIMINATED • REDUCED WEAR • APPLICATIONS • ENGINES • AUXILIARY GENERATORS • REFRIGERATION UNITS • COMPRESSORS Active Noise Cancellation

  16. AT THE EAR: SELECTIVE HEADSET(NARROW BAND NOISE CANCELLATION) "A SELECTIVE NOISE CANCELING HEADSET CAN IMPROVE WORKER SAFETY BY ENHANCING PERCEPTION OF WARNING SIGNALS" Active Noise Cancellation

  17. AT THE EAR: HEADSET(CONTINUED) • CHARACTERISTICS • SELECTIVE • REDUCE TONAL COMPONENTS TO THE BACKGROUNDNOISE LEVEL • BENEFITS • SAFETY • HEARING PROTECTION • COMFORT • APPLICATIONS • EQUIPMENT OPERATORS (IN-CAB) • GENERAL WORK SITE Active Noise Cancellation

  18. Speakers ResidualMicrophones Equalizer Analog Heaset(Broadband Noise Cancellation) An open-back, analog, noise canceling headset has good low-frequency attenuation and passes higher frequencies without attenuation. Active Noise Cancellation

  19. Zone Cancellation(Interacting Channels) "PLACEMENT OF SPEAKERS AND MICROPHONES REQUIRES CAREFUL ACOUSTICAL ENGINEERING TO PRODUCE A WELL BEHAVED SYSTEM" Active Noise Cancellation

  20. Saab 2000 Turboprop The SAAB 2000 aircraft (50 passengers) has an ANC system for reducing the noise in the cabin. http://www.ultraquiet.com This is achieved by measuring the sound with microphones (green) and generating canceling sound waves using speakers (red). The ANC system has 72 microphones and 36 speakers (a complex multivariable problem). A key advantage is a dramatic weight savings compared to passive treatments alone. Sonograms (a graphical representation of sound) left shows sound levels within the aircraft while in flight. Blues and greens represent lower levels, oranges and reds are higher. OFF ON Active Noise Cancellation

  21. Zone Cancellation(CONTINUED) • CHARACTERISTICS • EFFECTIVE ON TONAL NOISE BELOW 250 HZ • SOPHISTICATED ALGORITHM COMPENSATES FOR INTERACTIONS AMONG MICROPHONES AND SPEAKERS • BENEFITS • COMFORT • SAFETY • HEARING PROTECTION • APPLICATIONS • EQUIPMENT CAB (In production turboprop aircraft) • SITE OFFICE Active Noise Cancellation

  22. NOISE CANCELLATIONSUMMARY • PRACTICAL SOLUTION TO SELECTED REAL WORLD PROBLEMS • SIGNIFICANTLY REDUCES NOISE AND VIBRATION • COSTS ARE OFTEN COVERED BY IMPROVED EFFICIENCIES • SAFETY • ACCIDENTS • HEARING PROTECTION • PRODUCTIVITY GAINS • Better Communications • Better Throughput • Energy Savings Active Noise Cancellation

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