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| ELECTRONIC | FLOW CONTROL |
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| Use:
To cancel unwanted noise energy through destructive interference by
electronically generating a 180° out of phase anti-noise which is
equal and opposite in phase and amplitude.
Physical Properties: Equipment includes an input microphone, controller/amplifier, speakers and an error microphone. Works best with noise propagated in a confined/closed loop space such as a pipe or duct. Works best where the noise source is repetitive and not random. Works best in low frequencies up to about 500 Hz. Effectiveness is expressed as Dynamic Insertion Loss (DIL) for active/electronic mufflers and silencers. DIL: The noise reduction of sound power level attained by inserting a silencer or muffler in a pipe or duct transmission system under air flow conditions. Technological Advances: Electronic or active noise and vibration technologies are emerging from research and development to production applications. Recent advances include cancellation headsets, mufflers for automotive and industrial and a variety of consumer appliances. |
Use:
To reduce flow/fluid-borne noise transmission traveling through pipes
and ducts connected to air/fluid control devices, equipment and systems.
Mufflers or silencers use absorptive and reactive designs to allow
air passage while attenuating the noise. Fluid-borne flow systems
may be air, gases or steam.
Physical Properties: Internal geometry of the flow control device dictates the overall noise reduction that can be achieved and the resultant pressure loss of the system. Absorptive designs can vary the insulation thickness and density in the wall cavity as well as the distance between internal baffles (passage width). Reactive designs can vary the flow control device internal chamber length and volume as well as the number of interconnected chambers and the size and length of choke tubes connecting the chambers. Effectiveness is expressed as Dynamic Insertion Loss (DIL) for mufflers and silencers. DIL: The noise reduction of sound power level attained by inserting a silencer or muffler in a pipe or duct transmission system under air flow conditions. |
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Noise
and Vibration Control, Inc.
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1-610-863-6300
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