Source document: https://docs-lawep.s3.us-east-2.amazonaws.com/1697809113325.pdf (Mauritius)
ANNEX 14 Noise propagation sheet 1.

Outdoor sound propagation Sound pressure is inversely proportional to distance Therefore: P2 = p1 * r1/r2 ….. Eqn 1 Where: p1 = sound pressure 1 at monitoring station in Pa p2 = sound pressure 2 at a distance r2 from the sound source in Pa r1 = Distance between monitoring station and sound source in Pa r2 = Distance r2 from the sound source Sound pressure level, L: L = 20 Log10 (P rms)/(P ref) ….
Eqn 2 Where: L = Sound pressure level P rms= Effective sound pressure (root mean square) P ref = 20µPa Sample calculations From Eqn 2 L1 =20 Log 10 (p1)/(20 * 10-6) Let: L1 = Average noise level recorded at monitoring station 1 = 90 dB P rms = P1 Replacing values in Eqn 2, p1 = 0.63 Pa From Eqn 1 P2 = 0.63 * r1/r2 Let : 1 r1= 1m and r2 = 100m Therefore: P2 = 0.63x (1/100) = 6.3 * 10-3 Pa L2 = 20 Log 10 (6.3 * 10-3)/ (20 *10-6) = 50 dB Table 3: Estimation of noise propagation within 1km radius from the proposed site Distance (m) Sound pressure in dB in free field 90 50 44 40 37 36 34 33 32 31 30 1 100 200 300 400 500 600 700 800 900 1000 Limitations: 1.
It was assumed that there is no reflective surface in the sound field.

In the presence of reflective surfaces in the sound field, then reflected sound will add to the directed sound and more sound will be transmitted than inverse law predicts 2.

Physical barriers between the source and point of measurement were not taken into account.

3.

Ground configuration, terrain profile and wind turbulence were not taken into consideration.

2