Lecture-01-09-08 - MECH 668 Vehicle Noise Vibration and...

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MECH 668 Vehicle Noise, Vibration and Harshness (NVH) Fundamentals of Sound and Vibration Winter 2008
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2 Harmonic Motion ) t sin( A M ) t ( X φ + ω + = Amplitude (max response) Frequency (rad/sec) Time (sec) Phase (rad) Mean Value Mean Value Mean Value
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3 Complex Vector Representation ) sin( j ) cos( e where Be ) t ( X ) t sin( A ) t ( X j ) t ( j α + α = = φ + ω = α φ + ω
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4 Fundamentals of Sound Waves Spatial Distance, d Time, t Sound Pressure, P One wavelength, λ Period, T f 1 T , f 2 ), t sin( P ) t ( P s / m 344 , Wavelength c , sound of Speed ) Hz ( f , Frequency max = π = ω ω = λ = λ = One wavelength, λ (m) Frequency, f (Hz) 10 20 50 100 200 500 1k 2k 5k 10k 20 10 5 2 1 0.5 0.2 0.1 0.05 2 P dt ) t ( P T 1 P , Pa 20 P , P P log 10 dB 2 max T 0 2 rms ref 2 ref 2 rms = = μ = = Sound Waves in air (longitudinal type) Propagation Direction 2 2 2 2 2 x p c t p : wave plane D 1 =
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Plane Wave Solution – Induction/Exhaust Pipe ) kx t ( j ) kx t ( j 2 2 2 2 2 e A e A ) t , x ( p x p c t p : wave plane D 1 + ω ω + + = = Positive traveling wave Wavenumber K=2 π / λ Negative traveling wave f 2 2 k f c π = ω π = λ λ = ) x ct ( k kx ft k kx ft 2 kx t ) x ct ( k kx ft k kx ft 2 kx t + = + λ = + π = + ω = λ = π = ω ) x ct ( jk ) x ct ( jk e A e A ) t , x ( p + + + = 2 12 2 / 10 ; log 10 m watt I I I L c p Area W I Intensity Sound
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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-01-09-08 - MECH 668 Vehicle Noise Vibration and...

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