Download - NOISE CANCELLATION DoctorD.WebHop.Net

Transcript
Page 1: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 1

NOISE CANCELLATIONhttp://DoctorD.WebHop.Net

• INTRODUCTION

• TECHNOLOGY

• APPLICATIONS

• DEMONSTRATION

• SUMMARY

Page 2: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 3: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 4: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 4

NOISE CANCELLATIONTECHNOLOGY

• 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 APPROACHES

BROAD BAND - ADAPTIVELY FILTER THE SIGNAL FROM AN "UPSTREAM" SENSOR TO CREATE

THE ANTI-NOISE SIGNAL

SYNCHRONOUS - ADAPTIVELY SYNTHESIZE ANANTI-NOISE SIGNAL WITH A-PRIORI KNOWLEDGE OF THE BASIC "NOISECYCLE" RATE

– EFFECTIVE AT LOW FREQUENCIES

"A GOOD SOLUTION USUALLY REQUIRES A COMBINATION OF PASSIVE AND ACTIVE TECHNIQUES"

Page 5: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 6: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 7: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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

Page 8: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 8

Vacuum Muffler• Application: 100 horsepower diesel vacuum.

Used to load and unload railroadcars (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.

Page 9: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 9

Vacuum Muffler (Continued)

Condition Noise Back Pressure Note

Original 115 dBA 3 inches of Mercury Blower operates at 15 inches of mercury

Active System

91 dBA None 24% Fuel Savings20% Faster

“The quiet system loads/unloads a rail car 20% faster than the noisy system it replaced.”

Page 10: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 10

CSX MasterVac

Page 11: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 11

Diesel Engine Muffler

• Application: 450 horsepower diesel engine. 522 in3, 2-strokeUsed 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.

Page 12: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 12

Diesel Muffler Results(Demonstration Audio)

Condition Noise Back Pressure Note

Straight Pipe

123 dBA None 2 meters from the exhaust

Original Muffler

89 dBA 1.5 inches of Mercury

12 ft long2 ft diameter

Active System

81 dBA None 2% Fuel Savings20% Smaller

“The Active muffler system is 20% smaller than the conventional passive muffle it replaced.”

Page 13: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 14: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 14

CONTROLLING VIBRATION

"CONTROLLING VIBRATION NEAR THE SOURCE CAN GREATLY REDUCE ACOUSTICAL NOISE AND REDUCE WEAR"

Page 15: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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 - VIBRATION REDUCED

– SECONDARY ACOUSTICAL NOISE ELIMINATED– REDUCED WEAR

• APPLICATIONS– ENGINES – AUXILIARY GENERATORS– REFRIGERATION UNITS– COMPRESSORS

Page 16: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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"

Page 17: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 17

AT THE EAR: HEADSET(CONTINUED)

• CHARACTERISTICS– SELECTIVE– REDUCE TONAL COMPONENTS TO THE BACKGROUND

NOISE LEVEL

• BENEFITS– SAFETY– HEARING PROTECTION– COMFORT

• APPLICATIONS– EQUIPMENT OPERATORS (IN-CAB)– GENERAL WORK SITE

Page 18: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 18

Analog Heaset(Broadband Noise Cancellation)

An open-back, analog, noise canceling headset has good low-

frequency attenuation and passes higher frequencies

without attenuation.Equalizer

Speakers

ResidualMicrophones

Page 19: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 19

Zone Cancellation(Interacting Channels)

"PLACEMENT OF SPEAKERS AND MICROPHONES REQUIRES CAREFUL

ACOUSTICAL ENGINEERING TO PRODUCE A WELL BEHAVED SYSTEM"

Page 20: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg Active Noise Cancellation 20

Saab 2000 TurbopropThe 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.ON

OFF

Page 21: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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

Page 22: NOISE CANCELLATION DoctorD.WebHop.Net

J. N. Denenberg 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