hvac "wind" noise

Hello all, The studio at the university I teach at has an acoustic tile drop ceiling with hvac entering in 2 locations with the standard 2x2 plastic air diffusers covering the duct. Is there a solution out there that will reduce the "wind" noise I am getting from the hvac, or something that will redirect the air flow so I can place mics out of the path of the hvac? There is a good improvement just by removing the plastic diffusers, but the university is equally concerned with the appearance as they are with the sound. Anyone know of a good product for this? Thanks.

A silencer (baffle box) would be typical, but there may already be one in the system (above the ceiling) so check. Otherwise, increasing the duct size (or number of openings) and or using different diffusors / deflectors.

Thanks BriHar. Above the acoustic tile is 2 layers of drywall that is sealed around the ducts. My only options are products that would redirect the wind noise away from my mics, or no diffuser at all, which does seem to reduce the wind noise, but doesn't meet my boss's standards for appearance.

Are the ducts lined with proper duct-liner? If not, you might want to consider that. You should also check for obstructions inside the duct, with the first few feet of the diffuser. Look for things sticking out into the air stream, and see if you can get rid of those. The noise you are hearing comes form the turbulence generated when the air flow suddenly changes direction and speed as it is forced past obstructions, such as brackets, screws, dents, .... and poorly designed diffuser grills. There might also be a control damper just up-stream that is causing turbulence and therefore noise: try adjusting that so it provides the least possible restriction to air flow. However, be aware that you might be messing with other things in the system by fiddling with dampers, but it's worth a try. However, the basic issue here is that your HVAC system is incorrectly designed for a studio application. The flow rate should be slow enough that it does not create noise, there should be silencers (like Brian mentioned), there should be a "funnel" shaped expansion section just prior to the diffuser grill, several feet long, to slow down the air flow and reduce noise, there should be large plenums in the system close by that also slow down air flow. Several other things should have been done too, and apparently were not. Your last line of defence might be to just swap the diffuser for a low-noise model. There are some special-purpose diffuser grills that minimize air flow noise, and are designed specifically for studio use. They might be worth considering. Look for local HVAC suppliers in your area, and ask for recommendations on locally available low-noise grills, registers, diffusers. However, if the noise is caused by a badly designed system, then their isn't much more than this that you can do simply: the real solution is to fix the problem with the bad design. Open up the ceiling, take out whatever was done wrong, put in what needs to be there to do it right, then put the ceiling back in. Not cheap, but it might be your only real solution. Or maybe find another room in the building that does not have the noise issue? - Stuart -

Thanks Soundman2020. I am aware that the hvac is not properly designed for a studio. Without going into too much detail, this is a situation where I have to make the best use of the existing system. The noise is not unbearable, I am just looking for any modest improvement.

Check with your maintenance people or whoever would be knowlegeable, to see if there would be a way to reduce the amount of air flowing into the room either by reducing the overall capacity, or by using a duct regulator or diverter at or near the main unit. It is the volume of air being ducted at too high velocity or forced through vents that are too small (hence why removing the diffusers helps) that is causing your noise. You need to reduce this pressure.