### Strutt Help

Isolation Attenuation
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**Strutt|Vibration|Isolation Design|Isolation Attenuation** calculates the vibration isolation performance of a vibration isolator by modelling it as a lumped mass spring-mass-damper system

The force transmissibility ratio `TR` is calculated as:

`TR=sqrt((1 + (2 * zeta * (f/f_0)) ^ 2) / ((1 - (f/f_0) ^ 2) ^ 2 + (2 * zeta* (f/f_0)) ^ 2))`

where:

`zeta` is the damping ratio of the system

`f` is the input frequency

`f_0` is the natural frequency of the system

If the user selects to show units in dB, the `TR` is converted to dB as follows:

`Delta L_("isolation")=20log(TR)`

Reference: Ogata, K (2004) *System Dynamics*, Fourth Edition, eq 9-14

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