Patent ID: 6851514

Claim:
A sound attenuating duct unit suitable for connection to an airflow outlet of a machine having a rotating axial flow member and comprising: a duct housing having exterior sides and two opposite ends, an air inlet in one of said ends of said housing, and first and second air outlets with said first air outlet located at the other end of said housing, said air inlet being adapted for connection to said airflow outlet of said machine; interior walls arranged in said housing and defining a main airflow passageway system which extends from said air inlet to both of said first and second outlets; sound absorbing and thermal insulation material arranged between said interior walls and said exterior sides of the duct housing; sound attenuating members mounted in said airflow passageway system and comprising a series of splitters rigidly mounted in said airflow passageway system and dividing said main airflow passageway system into smaller passageways, each of said splitters having an exterior formed of perforated sheet metal and being filled with sound attenuating material, said perforated sheet metal having a thickness of at least 12 gauge, a layer of stainless steel screen being arranged behind the perforated sheet metal of each of said splitters and acting to prevent escape of the sound attenuating material; and a diverter damper mounted in said duct housing and movable between a first position where said damper directs air flow entering through said air inlet to said first air outlet and a second position where said damper directs said air flow to said second air outlet, wherein said sound attenuating members are mounted between said diverter damper and said air inlet so as to reduce sound levels emitted through either of said air outlets during use of said duct unit.