How do you calculate vibration isolation efficiency?

Divide the vibration velocity removed by the isolator by the incoming velocity at the mount. With 0.18 in/s removed from a 0.25 in/s input, efficiency is 0.18 / 0.25 = 72%.

What is a good vibration isolation efficiency?

Most precision and HVAC mounts target 90-98%. General machinery often specifies 70-85%; the 72% in the worked example clears a 70% spec but falls 2 points short of a 70%... note: it actually exceeds 70%, the gap shown is against a higher 70% target context.

Why is my isolation efficiency negative or below the target?

A gap of -2 points means you measured 72% against a 70% bar, so you are actually ahead. A truly negative efficiency means the isolated side reads higher than the source, which signals resonance amplification at the mount's natural frequency.

Isolation efficiency vs transmissibility, what is the difference?

Transmissibility is the fraction that passes through (0.28 here); efficiency is the fraction blocked (0.72, or 72%). Efficiency = 1 - transmissibility.

Does this account for different vibration frequencies?

No. It uses a single overall velocity value. For tonal problems, run an FFT and check efficiency band by band, because isolators amplify near resonance.

What units should I use for the readings?

Both vibration values must share the same unit, here in/s peak velocity. Mixing peak with RMS or velocity with acceleration will give a meaningless percentage.

Acoustic, Noise, Vibration & NVH Products calculator

Vibration Isolation Efficiency Calculator

Vibration isolation efficiency tells you what fraction of incoming vibration energy your isolators, mounts, or floating floor actually strip out before it reaches the protected structure. NVH engineers and machinery installers use it to verify that spring mounts, elastomer pads, or pneumatic isolators are doing the job specified in the equipment data sheet. It matters because an under-performing isolator transmits vibration into the building slab or chassis, where it re-radiates as structure-borne noise and shortens bearing and fastener life. The number is read straight from before-and-after velocity measurements taken with an accelerometer, so it reflects the real installed condition rather than a lab rating.

What this calculator does

Calculate isolation efficiency from reduced vibration level versus incoming vibration level and compare with a target.
an NVH engineer or facilities manager needs a quick percent isolation check from measured vibration levels
It computes isolation efficiency as the vibration velocity removed divided by the incoming velocity, then subtracts that from your target to show the gap in percentage points.

Formula used

Isolation efficiency = vibration reduced ÷ incoming vibration level
Gap to target = target isolation efficiency - isolation efficiency

Inputs explained

Vibration amplitude removed by isolators:
Incoming vibration at the mount:
Target isolation efficiency:

How to use the result

Use it after installing or tuning machine isolators when you have paired vibration readings on the source side and the isolated side of the mount.
Single-number velocity efficiency hides frequency content, so an isolator can read well overall yet still pass a problem tone near its natural frequency.

Common questions

How do you calculate vibration isolation efficiency? Divide the vibration velocity removed by the isolator by the incoming velocity at the mount. With 0.18 in/s removed from a 0.25 in/s input, efficiency is 0.18 / 0.25 = 72%.
What is a good vibration isolation efficiency? Most precision and HVAC mounts target 90-98%. General machinery often specifies 70-85%; the 72% in the worked example clears a 70% spec but falls 2 points short of a 70%... note: it actually exceeds 70%, the gap shown is against a higher 70% target context.
Why is my isolation efficiency negative or below the target? A gap of -2 points means you measured 72% against a 70% bar, so you are actually ahead. A truly negative efficiency means the isolated side reads higher than the source, which signals resonance amplification at the mount's natural frequency.
Isolation efficiency vs transmissibility, what is the difference? Transmissibility is the fraction that passes through (0.28 here); efficiency is the fraction blocked (0.72, or 72%). Efficiency = 1 - transmissibility.
Does this account for different vibration frequencies? No. It uses a single overall velocity value. For tonal problems, run an FFT and check efficiency band by band, because isolators amplify near resonance.

Last reviewed 2026-05-12.