Lecture_02-04-08 - 1 MECH 668 Vehicle Noise, Vibration and...

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Unformatted text preview: 1 MECH 668 Vehicle Noise, Vibration and Harshness (NVH) Duct Acoustics Read Chapter 3 Winter 2008 2 Flow Related Noise Sources in Vehicles Intake noise x x Exhaust noise x x HVAC noise x Wind noise x Exterior noise Interior noise 3 Intake & Exhaust System Design Issues Engine performance Packaging Cost and manufacturing Noise and vibration 4 Primary noise source unsteady mass flow through the valves causing pressure fluctuations in the intake ducts and exhaust pipes, which are also amplified by acoustic cavity resonances. Secondary noise sources flow noise created by motion of the flow through the intake and exhaust pipes. Breakout noise noise radiated from the intake and exhaust structures due to dynamic fluid-structure interaction. Intake/Exhaust Noise Sources Breakout noise Engine Exhaust Intake 5 Intake & Exhaust Airborne Noise Spectrum Dominated by acoustic cavity resonances (pipes, chambers, etc.) Highly tonal behavior (i.e. narrow-band peaks) Dominant frequency range is reasonable low, i.e. below 1000 Hz Noise control is usually done by tuning duct dimensions, and adding silencers, Helmholtz resonators and porous materials Design analysis approaches experimental and computational (frequency or time domain method) Fig 3.19 - Intake Noise Fig 3.20 - Exhaust Noise 6...
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This note was uploaded on 10/13/2010 for the course MECH 668 taught by Professor Lim during the Winter '08 term at University of Cincinnati.

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Lecture_02-04-08 - 1 MECH 668 Vehicle Noise, Vibration and...

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