# Determine the pump noise level

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 conversion 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 79. That means 79 dB(A) at 0 meter distance from the pumpset. If we then compare at a distance of 10 meters away from the pumpset, then the calculation is:

LWA-value:   79 dB(A)
Distance:     10 meters
Correction:    -29,0

Sound pressure level Lpa of the pumpset at 10 meters is 50 dB(A).

To determine the sound pressure of a pumpset for distances of 20 meters or more, a decrease of 3 dB(A) per distance doubling can be assumed.

## 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. 