hello /diy/,need ideas for creating a solution for this air vent i got in a place i just rented.
place Will be a workshop/music studio. vent is in a basement that i Will use only for making music when its very late. its not in the best shape, has humidity (natural, coming from the walls).

info: as you can see in pic related it goes directly to a sidewalk (quiet stret), when it rains some drops go in (not much).
the goals:
1- that it can be used with an air extractor (to reduce humidity and just move air in the whole thing)
2- that it can be blocked for soundproofing when im doing music (so sound doesnt go to the Street).
3- that i can prevent wáter from coming in when it rains.

cheap solutions are preffered but im open for well made stuff (thats why im here).
my take (mainly because of ignorance), would be:
1- conecting a air extractor with a round flexible duct (just using wires or something)
2- puting some sponge, it could be cutted to a shape that when compressed holds there
3- putting a metal sheet with some raisers so air goes, like a Little roof/table, where i can put plants on top

i also have no idea of the extractor i Will use, was just planning on searching for a used one (that is in almost new condition).
any idea or tip is wellcomed.

not even one tip or idea?
maybe its a boring problem i have, cheers board

It's a slow board. These are a refuge from bots and other scum of the internet.

I would build a wall. It can be as simple as covering with a sheet of plywood. Or it can be 4'x3' frame with sheets on both sides. I would construction adhesive fully around to the concrete to both support and so seal for audio. I would have a cut-out that I could either connect a fan of your choice (bath fan, dehumidifier, ac) or close for better sound iso.

I'd have to use a prybar and a grinder with metal brush to remove the adhesive on moveout if it's that important.