Every rotating pump makes a noise. For sources of noise which are emitted in the open air, the sound level decreases by 6 dB (A) when the distance is doubled. The table shows the change in the noise level at different distances from the source.

¹This conversion table is based on the following empirical formula for calculating sound pressure levels of semi hemispheric sound emittance 
LWA = LPA + log 4πR2 – 2. Here LWA is the sound power level and LPA is the sound pressure level at distance R (in meters) from the source. This formula holds for free field conditions.

Pump noise level calculation example

For example, if we use a diesel driven pump as the source of the noise, this has an LWA value of 90. That means 90 dB (A) at 0 meters distance from the pumpset. If we then compare at a distance of 33 feet (10 meters) away from the pumpset, then the calculation is:

LWA-value:  90                    
Distance:  33 ft (10 meters)
Correction: -28,0 dB(A)

Noise level of the pumpset at 33 ft (10 meters): 62 dB(A)

Explanation of used abbreviations

• LWA is sound power level and is measured and calculated according to ISO 3744:2010.
• LPA is sound pressure level and is determined using corrections according to the conversion table.
• dB(A) is the unit in which the strength of sound is represented in the vast majority of cases. The dB(A) is derived from the common decibel, but corrects sound strengths for the sensitivity of the human ear.