SONES

A sone is a measure of loudness. The higher the sone rating the louder the sound.

Understanding how loud an exhaust fan will be can be difficult, largely because bathroom exhaust fans are measured in sones, while most common noise levels we are familiar with are measured in decibels. Scientifically, one sone equals 40 phons, which is the loudness of a 1,000 hertz tone at 0 decibels above our threshold hearing level. The relationship between phons and decibels is not one-to-one (affected by, for instance, frequency), but for our purposes we will assume that decibels are roughly equivalent to phons. The chart below compares the sound level of a sampling of exhaust fans with the sound level of a number of other common sounds.


Sone
 
0.3
Panasonic 60 cfm FV05VQ2 Fan
0.5
30 Phons
0.5
Rustling Leaves
1.0
40 Phons
1.0
A Quiet Refrigerator
1.5
Panasonic 100 cfm FV11VQ2 Fan
2.0
50 Phons
2.0
Quiet Home
3.0
Panasonic 380 cfm FV40VQ3 Fan
3.0
Normal Office
4.0
60 Phons
4.0
Nornal Television Volume

Note that two sones are twice as loud as one sone, three sones are twice as loud as two sones, four sones are twice as loud as three sones, and so on.