Body Shell Rigidity
 

Car and Driver lists the Crossfire body-shell rigidity as "somewhere north of 51 Hz", and that it was significantly higher than the SLK. I also found a refernce to the BMW Z3 at 18 Hz, and the BMW Z4 at 21 HZ.
Can anyone tell me what would be considered bad, good, or great, and how one tests for such a thing?

I read the same article in C&D and never heard of body ridigity expressed in hertzs. Must have something to do with ability to dampen or not transmit vibrations through the chassis. Maybe an engineer will chime in and explain. Compared the Crossfire favorably with an Abrams tank which must be some sort of a compliment.

Vibrations travel through a vehicle's structure similar to the way radio waves travel through the air.Sound and vibration waves are measured in hertz.They have test equipment with sensors that can be hooked to the body and read the vibration frequency.I'm not sure what they consider a good reading. I'm asuming 51 HZ is good ??

If (according to Edmunds reviews) the Z4 and the Crossfire handle so similarly, why should the frequencies tested be so different?