<div class="htmlview paragraph">A novel method for evaluating the source flow ripple and source impedance of positive displacement hydraulic pumps is described. The method is based on the measurement and frequency domain analysis of pressure standing waves in a pipe, and uses a secondary source of pressure ripple for excitation of the pump under test. The method is convenient, accurate and versatile and forms the basis of a new British Standard for measurement of a pump fluid-borne noise rating. Representative results are presented for an oil hydraulic pump and for a plunger pump for water-based fluid.</div>