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 an internationally recognized unit of loudness. Sones are a linear measure like inches. Doubling the Sone value is equivalent to doubling the loudness. To get a sense of what one Sone represents, one Sone is equivalent to the sound of a quiet refrigerator in a quiet kitchen. 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!