Sones are a measure of volume similar to decibels, but specific to exhaust fans (from small bathroom fans to large ventilation equipment). Any given vent hood’s sone rating will offer a ballpark for how loudly or quietly they’ll run. To contextualize this: quiet refrigerators settle around 1 sone, light rain would fall around 3-4 sones, and regular conversation with background noise tends to begin around 6-7 sones.