When the impeller is driven by the pump shaft high speed rotation, the blade and the blade is driven by the role of force between the water, will be applied to the mechanical energy transfer to the cast of the water. When the impeller to rotate, the circumferential speed of the blade flow particle along the radius direction is getting more and more, in gradually increasing the action of the centrifugal force, basically along the radial flow impeller, and was thrown to the exit of the impeller, so that the water is gaining momentum. Due to the limited number of water pump impeller blade, formed in a circumferential direction of the impeller outlet pressure distribution, when the water cycle through guide leaf import or volute chamber separation tongue position, the pressure variation of the height of the passes to the water side pressure, the pressure pulsation produced the pump body of the noise and the water outlet pipe of the pump shell vibration. At the same time in the impeller, guide vane, the inside of the pump shell, the whirlpool is unavoidable, especially in the state far away from the pump operating point for design, the swirling irregularly recurring, disappear, can produce noise and vibration.
Pump noise spectrum was intermediate frequency characteristics, high frequency sound is small, at 31.5 ~ the low-frequency 125Hz often have a peak, the sound pressure level general in 85 ~ 101dB, along with the increase of the rotational speed, the head, the noise level also increased.
