The effect of vibration isolator properties and structural stiffness on isolator performance

The structural stiffness above and below a vibration isolation mount has an important effect on isolator performance. Knowledge of these as well as isolator properties is necessary to be able to predict the insertion loss of an isolator and the transmitted power to the foundation. A set of generalized mobility equations is used to analyze both the single-connection point and multiple-connection points cases. Experimental methods for determining the four-pole parameters, which describe the frequency-dependent dynamic properties of a vibration isolator, are discussed, and the test facility developed by the authors for the measurement of four-pole parameters is described. Test results for a commercially available isolator are presented. The importance of the structural dynamic properties above and below the isolator is illustrated by calculating the isolator effectiveness for different foundation properties.