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Random Vibration transmissibility

Random Vibration transmissibility

Random Vibration transmissibility

I have some Random Vibration test results. The curves I have give me the input level at the I/F (g^^2/Hz) and the transmissibility at a point on the structure. I have to find the vibration level (g^^2/Hz) at that point. Do I just take the transmissibility and multiply with the g^^2/Hz. input level??????

Thanks for any hints


RE: Random Vibration transmissibility

I think the answer is yes, but I'm sucking my teeth at this, transmissibility isn't a simple concept, until you define the input and output impedances.


Greg Locock

RE: Random Vibration transmissibility


the only question is, is your data MOTION transmissibility or FORCE transmissibility ?

If it is the first case (which is highly likely), you can get you output PSD simply by multiplying the input PSD by transmissibility.

If it is not the case, the you can convert you force transmissibility (Fout/Fin) to motion transmissibility (Xout/Xin) using impedance (F/velocity) curves.

How was that transmissibility measured? (Beware that transmissibility is defined BETWEEN two points, at not AT a point. On the contrary, impedance is defined AT a point F/v, at the same point).

Refer to the "Handbook of Shock&Vibration (Harris, editor) for more details.

Hope this helps

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