The Hakko® Silencer reduces the sound to 1/5 of the sound of an HJ3100 fume extraction unit (8 dBA across the audible frequency band.) It is particularly effective against high frequency noises, which are more irritating than low frequency noises. The Silencer attaches to the exhaust grill on the HJ3100. Airflow is reduced by approximately 10% (17 cfm.).