The New Silencer By Air Supply has taken a quantum leap in quiet performance. The unique motor mount is the secret to our success. A thick rubber cup encases the fan while allowing the motor to vibrate freely on a flexible rubber base. This combination eliminates noise so well that virtually no foam is required. Many competitive blowers uses filter foam to reduce noise, but foam may clog over time causing starvation and overheating.Included with each silencer is a durable spring check valve. This is far more effective than flapper valves at stopping motor damage, which means fewer service called and more satisfied customers. Air Supply is committed to quality and service.