Vibration Transmissibility Calculator

About this calculator

Transmissibility (TR) measures how effectively a spring-type mount isolates a vibrating machine from the structure it sits on. For the simplest case — an undamped single-degree-of-freedom isolator — it depends only on the frequency ratio r, the forcing frequency divided by the mount’s natural frequency: TR = 1/|1 − r²|. This calculator takes the forcing and natural frequencies, computes r, and returns TR.

The formula splits isolation behavior into two regimes that every mechanical engineer designing an isolation mount needs to know: when r is less than √2 (about 1.41), TR exceeds 1 and the mount actually amplifies vibration rather than reducing it — resonance at r = 1 makes this worst — while for r greater than √2, TR drops below 1 and the mount begins isolating, with transmissibility falling further as r increases. This is why isolation mounts are deliberately designed with a natural frequency well below the machine’s operating (forcing) frequency, and why the calculator flags whether a given setup actually isolates.