The fluid borne noise characteristics of hydraulic components and their measurement

  • Timothy John Wing

Student thesis: Doctoral ThesisPhD


This thesis is concerned with the development of test techniques for evaluating the fluid borne noise characteristics of components found in hydraulic systems; in particular the source impedance and source flow of positive displacement pumps.

A number of proposals for measuring the fluid borne noise generation potential of positive displacement pumps are critically reviewed. Particular attention is paid to the high impedance pipe technique which is to be proposed as a British Standard.

An apparently simple method of obtaining the source characteristics of a pump using only two transducers is shown to have serious drawbacks due to magnified errors at resonant line length conditions.

A computer based scheme, capable of predicting the source and termination characteristics of a pump-pipeline-termination system is developed. The scheme is iterative and based on fitting the surface of least squares error through a series of experimental pressure readings. The technique requires the pressure ripple to be measured at a number of points along a pipeline and for a series of different pipe lengths. A special rig has been designed and built to facilitate the data acquisition.

Using the technique, the source flow and source impedance characteristics of a number of axial piston and gear pumps are examined. The results obtained show very good agreement with theory and clearly demonstrate the effects of pressure and speed on the source flow.

The impedance of several terminations are also predicted. For an expansion chamber the predicted entry impedance is shown to deviate from simple theory and this is attributed to vibration of the chamber. The impedances of restrictor and relief valves are shown to be quite complicated frequency dependent functions and it is demonstrated that significant errors in pressure ripple prediction may result from the use of over-simplified models.

Date of Award1982
Original languageEnglish
Awarding Institution
  • University of Bath

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