tech drive super-quiet 110 cfm, 1.0 sone bathroom ventilation and exhaust fan (110cfm) tech drive <b>how to choose your bathroom fan?</b><br><br> <b> what is a sone rating?</b><br> sones, or the sone rating, is a term used to describe sound levels. lower sone ratings are found on quieter fans. higher sone ratings indicate a louder bathroom fan.<br><br> <b>what is cfm? </b><br> cfm (cubic feet per minute) measures fan air movement. cfm increases as air movement increases. a higher cfm is best for a larger bathroom; a lower cfm may be adequate for smaller spaces.<br><br> td-bf-01 110cfm/1.0sones. ventilating for bathroom up to 110 sq. ft <br> td-bf-02 90cfm/0.8sones. ventilating for bathroom up to 90 sq. ft <br> td-bf-03 70cfm/2.0sones. ventilating for bathroom fan up to 75 sq. ft<br>