I want to check the removed rubber isolation mount natural frequency. I have done the bump test by hitting at the top( Sensor also in vertical direction). The natural frequency indicated was 50 Hz. I again checked the new rubber mount also and i got the same value. Whether my procedure of measuring the natural frequency by hitting the top of the isolator is correct? If not, how can i verify / measure the natural frequency of rubber isolator mounts.Comments please.

A vibration isolator is primarily a spring element that should be part of a spring-mass system. Simply impacting an isolator by itself does not (cannot) provide a useful natural frequency. If you are really trying to test an isolator by itself, then you should measure static spring rate (weight/force and deflection).

Walt

Gevenag,
I fully agree with Walt.
Natural frequency and deflection when loaded are directly related:
frequency [hz] = sqrt(248/x) where x is deflection in mm (1 inch = 25.4 mm).
More [kg], [lbs] load -> lower natural frequency.
My pick-up also drives more comfortable the more potatoes are loaded.
Regards, Arie Mol, NL