The proportion of vibrational energy transmitted by a vibration Isolator is given by:
ff = forcing frequency of vibration (Hz)
fn = natural frequency of vibration isolator (Hz)
m = mass (kg)
c = viscous damping (Nsm-1)
ωn = 2 π fn
For lightly damped materials, such as steel springs, the critical damping ratio is negligible. The formula can then be simplified to:
This shows that when resonance occurs (ff= fn) T tends to infinity (i.e. there is significant amplification of the transmitted force rather than any isolation).
For isolation to occur T must be less than one, which only occurs when:
However, the actual performance of a vibration isolator can be compromised by several factors that must also be taken into account when designing or selecting a vibration Isolator [Find Out More].