ducts

[JORGE SANCHEZ]

I would like to know about flush and flared ducts.

[glen]

They are both doing the same job.
The flared mouth on some ports is designed to reduce the sometimes audible "huffing" sound as air moves in and out of the port.
By increasing the cross-sectional area at the mouth of the port the velocity of the air moving through it is slowed, so that there is less sound of rushing air without reducing the normal bass reflex function of the port.