It is the transfer function (in the frequency domain) of velocity to force, at a point, in the same direction. If you need more than that (I think you do) then you'd be better off asking in the FEA group.
Ah, perhaps I see. You need to apply a unit force spectrum to one direction of a node, as a dynamic analysis.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
I think there is a relationship between a NTF/VTF (noise transfer function/vibration transfer function and point mobility). Is it only because of the body sensitivities (resonances) or is there any other correlation between the two?
One way of looking at it is that the NTF needs a moving diaphragm to create noise, and the VTF shows the frequencies at which the structure is especially responsive, so there will be some correlation between the two.
I'm not sure if you meant NTF/VTF as a transfer function. That would be a very complex relationship, for a realistic structure, but very simple for a vibrating plate, where it boils down to P/V, which is a well known relationship.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
I meant VTF to PM and NTF to PM. VTF to PM seems reasonable. What about PM to NTF?
For NTF I assume you hit the structure with an impact hammer and collect the pressure at the drivers ear.
"I meant VTF to PM and NTF to PM. VTF to PM seems reasonable. What about PM to NTF?"
Well PM is just one VTF, so the same answer applies
"For NTF I assume you hit the structure with an impact hammer and collect the pressure at the drivers ear."
yup, or anywhere else. We've done acoustic modals of vehicles, collecting P/F for a grid throughout the cabin. We've also done P/V, using a loudspeaker as excitation.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
