Determine the pump sound 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 table shows the change in the noise level at different distances from the source.

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)

distance to heart sound source	Correction (c)
ft	dB(A)
3,3	8,0
6,6	14,0
9,9	17,5
13,2	20,0
16,5	22,0
19,8	23,5
23,1	24,9
26,4	26,0
29,7	27,1
33	28,0
49,5	31,5
66	34,0
82,5	35,9
99	37,5
115,5	38,9
132	40,0
148,5	41,0
165	42,0
181,5	42,8
198	43,5
231	44,9
264	46,0
297	47,1
330	48,0
363	48,8
396	49,6
429	50,3
462	50,9
495	51,5
528	52,1
561	52,6