Vibration Isolation Calculator

Real-time vibration isolation analysis based on first-principles SDOF theory. Formulas from Den Hartog and Thomson & Dahleh.

Engine & Mount Parameters

kg
rev/min
cylinders
mount points
N/mm (kN/m)
dimensionless (typ. 0.02-0.15 for rubber)

Presets

--
Natural Freq. (Hz)
--
Firing Freq. (Hz)
--
Freq. Ratio (r)
--
Transmissibility
--
Isolation %
--
Insertion Loss (dB)
--
Static Defl. (mm)
--
Load/Mount (kN)

Transmissibility Curve

Engine Excitation Frequencies

Order Frequency (Hz) Source Transmissibility Isolation % Insertion Loss (dB) Status

Isolation Design Rules

Formulas Reference

All calculations from first-principles SDOF vibration theory

Natural Frequency

f_n = (1/2pi) * sqrt(k_total / m)

Where k_total = N_mounts * k_per_mount (N/m), m = total supported mass (kg). Units: Hz.

Transmissibility

T = 1 / sqrt((1-r^2)^2 + (2*zeta*r)^2)

Where r = f/f_n (frequency ratio), zeta = damping ratio. T < 1 means isolation, T > 1 means amplification.

Insertion Loss

IL = -20 * log10(T) dB

Decibel measure of vibration reduction. 20 dB = 10x reduction, 40 dB = 100x, 60 dB = 1000x.

Firing Frequency

f_fire = RPM * N_cyl / (60 * stroke_factor)

stroke_factor = 2 for 4-stroke, 1 for 2-stroke. This is the dominant excitation frequency for reciprocating engines.