Plenum & Silencer for HVAC

Hi! can anyone explain the difference between a plenum & a silencer for HVAC system? As far as I'm aware ... a plenum takes a large duct - then spreads it to numerous smaller ducts just as plenum chamber on intake manifold of combustion engine. I take it this serves a different purpose than the silencer... just wondering if the two can be integrated into one single unit? ALSO: would the same be required for ventilation system ( i.e fans for air exchange ) ??? Can I run the ventilation system ( i.e fans for air exchange ) back into the Air Conditioner or am I better off keeping them separate ?? re: viewtopic.php?f=1&t=10426&p=104193#p104193

typically the "plenum" is the large part of duct work going into (or out of) the heating/cooling unit, or just a large section of duct. the "silencer" you might use in the plenum would typically be used to control the noise from the blower. for intra-room purposes, the silencer or baffle box would be used to ensure the isolation on a given room so it's not transferred via the duct to another room or elsewhere.