The noise of the HXHT fan was measured in a non-reverberant room with a background noise below 15dBA. The fan to be tested runs in free air, and a noise meter is disposed one meter away from the air inlet.
 
The sound pressure level (Sound Pressure Level) depends on the background factors, and the sound power level (Sound Power Level) is expressed by the following formula:
SPL=20logP/Pref
And SWL=10logW/Wref
P = sound pressure
Pref=reference sound pressure
W = noise energy of the sound source
Wref=noise energy of sound source
The noise value of the fan is usually plotted in the octave band of the sound pressure level (SPL). The effects of changes in decibels (dBA) are shown in the following signs:
3 dBA hardly feel
5 dBA felt
10 dBA feel twice as loud

Sound level:
0 ~20 dBA very weak
20~40 dBA weak
40~60 dBA Moderate
60~80dBA loudly
80~100 dBA very loud
100`140 dBA deafening