CFM stands for Cubic Feet per Minute of exhausting air flow. The higher the number, the greater the amount of air that is exhausted using the Range Hood.
A sone is a measurement of sound in terms of comfortable hearing level for an average listener. The lower the sone value, the more comfortable the listening environment. Sones are not decibels or volume, but rather how sound is "sensed".
1 Sone = The refrigerator running in your kitchen.
2 Sones = The noise level in an office workplace.
3 Sones = The level one would have in a face to face conversation.
4 Sones = The level that most listen to the TV in their home.
5 Sones = Noise level of a busy restaurant at dinner time.
6 Sones = Sporting event in an arena or stadium.
Note: Sones are a better measure than decibels because sones are linear (2 sones is twice as loud as 1 sone as opposed to decibels which are logarithmic - 66 decibels is twice as loud as 60 decibels).
Typically, the Sone level is measured at maximum CFM (speed), however, some newer products are also being tested at normal CFM (speed) settings to provide consumers with typical sound level information.
All Broan-NuTone CFM and Sone ratings are HVI certified so you can rely on them!