Depends how much air you need to move. For one person, a baffle of 10x 1cm sheets of plywood with a 2cm air clearance will do wonders (works out to be approx a

Depends how much air you need to move. For one person, a baffle of 10x 1cm sheets of plywood with a 2cm air clearance will do wonders (works out to be approx a 30cm cube with a 30x2cm slot at the front and back). You can push ample air for one into a studio without any audible sound getting through.