The measurement of positive displacement pump and motor noise using sound intensity techniques

The noise levels generated by a variable capacity axial piston pump and a fixed capacity axial piston motor have been measured using Sound Intensity techniques; no special acoustic test environment was employed. The experimental procedures followed, as closely as possible, draft International Standard ISO/DIS 9614-4. Because the machines were mounted on existing test stands it was found difficult to comply completely with the requirements laid down in the draft Standard. Typical test results are presented showing that pump overall Sound Pressure levels increase significantly with increasing delivery pressure. The effect of discharge pipe length on pump noise levels is relatively small. From the motor noise tests, it was found that variations in speed were much more important than load. The work has highlighted the need for the development of Sound Intensity procedures specifically concerned with fluid power pumps and motors.