The Sound Enclosure dampens the sound created by the blower package. STANDARD CONSTRUCTION FEATURES Corrosion-resistant aluminum construction4-Door entry provides easy access to the blower packageFlat, lift-off roofPSI #618 Composite acoustical foam featuring fire resistance, mold and mildew resistance and UV inhibitors. Also resistant to oil and other chemicalsSound attenuation tested from 20-30 dBA (testing required for performance guarantee)Acoustically engineered air inlet boxDrip edge for all weather installationsVentilator fan size based on heat load calculationsZinc-plated hinges and hardware