Control Valve Noise Summary

The requirement for noise control is a function of legislation to protect our wellbeing and to prevent physical damage to control valves and piping. Noise prediction is a well defined science. Actual results will be within 5 dBA of predicted levels.
Prediction is based upon contributions for:

1. Pressure drop
2.Flow rate
3.P/P1 and trim style
4.Piping and insulation
5.Downstream pressure

Noise reduction is accomplished in two general ways:
1. Source treatment, which acts upon the amount of noise generated.

Noise reduction is accomplished in two general ways:
1. Source treatment, which acts upon the amount of noise generated.
2. Path treatment, which blocks transmission on noise to the environment.

There are two common source treatments:

1. Valve noise trim is based on principles of dividing the flow to create many small noise
sources which combine to a lower level than a single large flow noise. Diffusers used with control valves share pressure drop creating two lower noise sources which again combine to an overall lower level.
2. Path treatment involves use of insulation or absorptive devices to lower the sound level which reaches observers.
Hydrodynamic noise from liquid flow streams can mainly be traced to cavitation. In this case,
damage from the cavitation is of more concern than the noise. Appropriate treatment of the
cavitation source should be initiated through staging the pressure drop.
Two-phase, or pure flashing, applications do not create noise problems, and there is no technically appropriate two-phase noise prediction method