The Effect of Vibration Isolator Properties and Structural Stiffness on Isolator Performance

Abstract

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 equa tions 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 proper ties 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.

Keywords

Isolators effectiveness insertion loss mobility

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References

Dickens, J.D. , Norwood, C.J. , and Juniper, R.G. , 1993, "Four pole parameter characterisation of isolator acoustic transmission performance," Australian Acoustical Society Annual Conference, Adelaide, Nov. 9-10.

Goyder, H.G.D. and White, R.G. , 1980a, "Vibration power flow from machines into built-up structures, part 1 Introduction and approximate analysis of beam and plate-like foundations," Journal of Sound and Vibration 68(1), 59-75.

Goyder, H.G.D. and White, R.G. , 1980b, "Vibration power flow from machines into built-up structures, part II: Wave propogation and power flow in beam-stiffened plates ," Journal of Sound and Vibration 68(1), 77-96.

Goyder, H.G.D. and White, R.G. , 1980c, "Vibration power flow from machines into built-up structures, part III: Power flow through isolation systems," Journal of Sound and Vibration 68(1), 97-117.

Harris, C.M. , 1987, Shock and Vibration Handbook, 3rd ed., McGraw-Hill, New York.

Jacobsen, F. and Ohlrich, M. , 1986, Vibrational Power Transmission From Multipoint Mounted Machinery to Supporting Structure, Acoustics Laboratory, Technical University of Denmark, report no. 35.

Meltzer, G. and Melzig-Thiel, R. , 1980, "Experimental determination and practical application of the four-pole parameters of structure-borne sound isolators," Archives of Acoustics 5, 315-336.

Molloy, C.T. , 1958, "Four-pole parameters in vibration analysis," in Mechanical Impedance Methods for Mechanical Vibrations, R. Plunkette, ed., ASME, New York.

Mondot, J.M. and Petersson, B. , 1987, "Characterisation of structure-borne sound sources: The source descriptor and the coupling function," Journal of Sound and Vibration 114(3), 507-518.

10.

Norwood, C. , 1987a, Vibration Isolator Properties and Performance Prediction, ⊘ degaard and Danneskiold-Sansoe, Copenhagen, report no. 87.199.

11.

Norwood, C. , 1987b, Finite Element Prediction of Driving Point and Transfer Mobilities for a Model Ship Structure, ⊘ degaard and Danneskiold-Sansoe, Copenhagen, report no. 87.197.

12.

Petersson, B. and Plunt, J. , 1982a, "On the effective mobilities in the prediction of structure-borne sound transmission between a source structure and a receiving structure, part I: Theoretical background and basic experimental studies," Journal of Sound and Vibration 82(4), 517-529.

13.

Petersson, B. and Plunt, J. , 1982b, "On the effective mobilities in the prediction of structure-borne sound transmission between a source structure and a receiving structure, part II: Procedures for the estimation of mobilities," Journal of Sound and Vibration 82(4), 531-540.

14.

Pinnington, R.J. and White, R.G. , 1981, "Power flow through machine isolators to resonant and non-resonant teams," Journal of Sound and Vibration 75(2), 179-197.

15.

Snowdon, J.C. , 1979, Vibration Isolation Use and Characterisation, Applied Research Lab, Penn State University

16.

Sykes, A. O., 1971, "Application of admittance and impedance concepts in the synthesis of vibrating systems," in Synthesis of Vibrating Systems, V. H Neubert and R. P. Raney , eds., ASME, New York.

17.

Ungar, E.E. and Dietrich, C.W. , 1966, "High frequency vibration isolation," Journal of Sound and Vibration 4(2), 224-241.

18.

Verheij, J.W. , 1982, Multi-Path Sound Transfer From Resiliently Mounted Shipboard Machinery, Institute of Applied Physics, TNO-TH, Delft, The Netherlands.