Standard-line pumps are generally not severe noise sources when the pumps
are operated at their rated speed and capacity. Noise from pumps involves
both hydraulic and mechanical sources. Some of the sources of noise
in pumps include cavitation, fluid pressure fluctuations, impact of solid
surfaces, and dynamic imbalance of the rotor. The hydraulic sources are
usually the more important noise generators, unless there is a mechanical
problem in the pump, such as imbalance of the rotor