Transmissibility

A ratio of response amplitude to imposed excitation amplitude in a vibration problem. One must specify the input and output: displacement transmissibility and force transmissibility are different measurements. For a base-excited oscillator whose spring and viscous damper both act relative to its support, complex displacement amplitudes obey $X/Y=(k+i\gamma \omega )/(k-m{\omega }^2+i\gamma \omega )$. Its magnitude is the displacement transmissibility. A damper fixed to the laboratory rather than the support has a different numerator, so the attachment geometry matters.