This part of ISO 10767 specifies a procedure for the determination of a rating of the source flow ripple, source impedance and pressure ripple levels generated by positive-displacement hydraulic motors, including bi-directional motors. Ratings are obtained as the following:

• the source flow ripple amplitude, in cubic metres per second, over ten individual harmonics of motoring frequency;
• the source impedance amplitude, in newton seconds per metre to the power of five [(N·s)/m⁵], and phase, in degrees, over ten individual harmonics of motoring frequency;
• the anechoic pressure ripple amplitude, in pascals, over ten harmonics of motoring frequency;
• the overall root mean square (r.m.s.) anechoic pressure ripple, in pascals;
• the blocked acoustic pressure ripple amplitude, in pascals, over ten harmonics of motoring frequency;
• the overall root mean square (r.m.s.) blocked acoustic pressure ripple, in pascals.

This part of ISO 10767 is applicable to all types of positive-displacement motor operating under steady-state conditions, irrespective of size, provided that the motoring frequency is in the range from 50 Hz to 400 Hz.