Fan Sound Formula

Addition of noise levels

Difference in added values          Value to add to highest

0 to 1                                                   3

2 to 3                                                   2

4 to 9                                                   1

10 and greater                                     0

Lp     Sound Pressure Level (dB)

Lw    Sound Power Level (db)

D      Distance (m)

Q      Surface Directivity (see below)

Q =   2 (Located close to 1 surface)

Q =   4 (Located close to 2 junction surfaces)

Q =   8 (Located close to 3 junction surfaces)