Vibration Isolation Calculator

Evaluate isolator stiffness, damping ratio, and forcing frequency. See resonance risk, deflection, and force transfer. Make steadier machine supports with clearer engineering decisions today.

Calculator Inputs

Reset

Example Data Table

These examples show how different stiffness and damping choices change transmissibility and transmitted force.

Case Mass (kg) Isolators Stiffness Each (N/m) Damping Ratio Excitation (Hz) Force (N) Transmissibility Isolation (%)
Pump Skid 120 4 180000 0.08 25 900 0.336 66.40
Compressor Base 250 6 220000 0.12 18 1500 0.726 27.42
Fan Unit 75 4 95000 0.05 30 500 0.172 82.81

Formula Used

Total stiffness:
ktotal = n × k
All isolators are assumed to act in parallel.
Natural frequency:
ωn = √(ktotal / m)
fn = ωn / (2π)
Frequency ratio:
r = f / fn
This compares operating speed to the system natural frequency.
Force transmissibility:
T = √[(1 + (2ζr)2) / ((1 - r2)2 + (2ζr)2)]
If T is below 1, less force reaches the support.
Isolation efficiency:
Isolation (%) = (1 - T) × 100
Static deflection:
δ = mg / ktotal
Displacement amplitude:
X = (F0 / ktotal) × [1 / √((1 - r2)2 + (2ζr)2)]
Transmitted force:
Ft = T × F0

How to Use This Calculator

  1. Enter the supported machine mass in kilograms.
  2. Add the number of isolators carrying the load.
  3. Enter the stiffness of one isolator in newtons per meter.
  4. Input damping ratio, typically from test data or catalog values.
  5. Enter the operating or excitation frequency in hertz.
  6. Enter disturbing force amplitude from imbalance or cyclic loading.
  7. Set a target isolation percentage for quick pass or fail review.
  8. Click calculate to see resonance risk, transmissibility, force transfer, and deflection above the form.

FAQs

1. What does force transmissibility mean?

It is the ratio of force reaching the support to the original disturbing force. Values below one indicate isolation. Values above one indicate amplification near resonance.

2. Why is the frequency ratio important?

The frequency ratio compares operating frequency to natural frequency. Isolation usually becomes effective when the ratio is greater than about 1.414 for lightly damped systems.

3. Is higher damping always better?

Not always. More damping reduces resonance peaks, but it can slightly worsen high-frequency isolation. Good design balances startup resonance control with steady operating isolation.

4. Why does static deflection matter?

Static deflection is linked to stiffness and natural frequency. Greater deflection usually means a lower natural frequency, which can improve isolation at higher operating speeds.

5. Can this calculator be used for rotating equipment?

Yes. It is well suited for fans, pumps, compressors, and similar machines where a repeating disturbing force acts through an isolated mount set.

6. What happens near resonance?

When excitation frequency approaches natural frequency, motion and transmitted force can rise sharply. Designers often avoid prolonged operation in this region.

7. Does the calculator assume equal load sharing?

Yes. It assumes each isolator shares the load evenly and acts in parallel. Uneven support conditions can change actual stiffness and performance.

8. What target isolation percentage is reasonable?

Common engineering targets range from 70% to 90%, depending on equipment sensitivity, foundation limits, and acceptable startup behavior near resonance.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.