What is a sones rating?

A sones rating is a measure of the sound level produced by a ventilation fan. It indicates the amount of noise generated by the fan in operation and is used to help customers choose a fan that will provide the right amount of ventilation without being too loud. The lower the sones rating, the quieter the fan will be. A sones rating of 0.5 or less is considered very quiet, while a rating of 4 or higher is considered noisy. Most bathroom and kitchen fans have sones ratings between 1 and 3. The sones rating system was developed by the HVI (Home Ventilating Institute) to provide a standardized way to measure and compare the sound levels of ventilation fans.