point mobility

[zerodof]

What is the physical meaning of point mobility and how do we set the targets at engine and suspension attachment points for c class BIW.
Has anybody got any figures??

Is it important to calculate the noise transfer funtion at the concept phase of BIW and if it is how do we calculate/predict noise transfer funtion using nastran and how to set the targets assuming no benchmarking data is available.

 

[GregLocock]

The physical meaning of point mobility is that it tells you how much velocity you can create at that point for a given force, at each frequency. Velocity is used for several reasons, not least of which is that sound pressure generated by a radiating panel is a function of velocity.

Typical targets are (from memory) around 10 mm/s/N

Calculating NTFs is very difficult. From the questions you are asking you are about 10 years away from needing to worry about being able to predict them in the absence of real data to compare them with.

The generic target for NTFs is about 0.02 Pa/N, or as they say 55 dB @ 1N

The paper that established these targets was written in about 1978, I think by some people at MIRA.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.