Vibration Isolation Transmissibility Calculator (Machine on Rubber Mounts)

What this tool does

A machine on mounts is a mass on a spring, and the mounts only isolate once the machine's speed is above √2 times the natural frequency; below that they amplify, with a peak at resonance (r = 1). Above √2 the transmissibility falls, so the usual rule is to choose soft mounts that put the natural frequency three or four times below the running speed. Damping lowers the resonance peak but slightly raises the transmitted force at high speed. Because the natural frequency depends on the static deflection (f_n ≈ 15.8 ÷ √δ in mm), a soft mount is just one that sags a lot.

Formula

f_n = (1 ÷ 2π) √(k ÷ m) · r = f ÷ f_n · T = √[(1 + (2ζr)²) ÷ ((1 − r²)² + (2ζr)²)] · isolation only above r = √2

Variables

Worked example

Limitations

• The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
• The formula assumes ideal conditions: no friction losses, no air resistance and no efficiency losses unless you enter them.