User manual

C. Useful Formulae and Tables C.5. AIR ATTENUATION
1k 10k 20k
−30
−25
−20
−15
−10
−5
0
frequency [Hz]
Attenuation [dB]
Attenuation of sound in air (50m)
20%
40%
60%
80%
Figure C.1: Attenuation in function of relative humidity at a distance of 50m.
This table presents some attenuation values, expressed in dB/km, for vaious levels of relative humid-
ity and at a temperature of 20
◦
C:
freq. [Hz] 10% 20% 30% 40% 50% 60% 70% 80% 90%
1 14 6.5 5 4.7 4.7 4.8 5 5.1 5.3
1.25 21 9.4 6.7 5.9 5.7 5.7 5.9 6.1 6.3
1.6 32 14 9.8 8.1 7.5 7.2 7.2 7.4 7.5
2 45 22 14 11 9.9 9.3 9 9 9.1
2.5 63 32 21 16 14 12 12 11 11
3.15 85 49 32 24 20 17 16 15 15
4 110 75 49 36 30 26 23 23 20
5 130 110 74 55 44 38 33 33 28
6.3 160 160 110 84 68 57 50 45 42
8 180 220 170 130 110 89 78 69 63
10 190 280 240 190 160 130 120 100 95
12.5 210 360 340 280 240 200 180 160 140
16 230 430 470 420 360 320 280 250 230
20 260 510 600 580 520 470 420 380 350
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