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I recently calculated the PSD of the vibration data in a car at constant speed. I would like to know what this means and what if I calculate PSD of the vibration data in a car for the total journey with varying speeds? What do both PSDs signify?

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I'll make a few guesses here. At a first look, I wouln't think speed would have much effect on the normal vibrational effects. At higher speed we have, greater torque and wind resistance, which would look like a slightly different external loading. More significantly, the wheels are rotating faster, and that probably modifies the normal modes spectrum somewhat. Lastly, the excitation comes from tire noise, and road imperfection (and maybe turbulent air flow), which presumably is skewed more towards higher frequencies at higher speeds.

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Thank you Omega.. –  Dilip Mar 15 '11 at 12:14

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