Whooshing noise means air ducts/vents are already too restrictive,farther restricting air flow can lead to serious damage. It sound's like not only was your kitchen sink oversized for a tiny house,the hvac was to.

You will always get wind noise when you use the vent to close off airflow. What you need (if you don't have it already) is a damper where the branch duct to the offending register comes off the main trunk line.

Hobie, is this a newer system? Regardless, I suggest that you bring pros to this. I had a situation with a new, energy efficient HVAC/duct system that was ridiculously loud- whooshing included. The installers started with some baffling right in the vents. Close, but no cigar... Then we upgraded our motor, and all was good. It cost us very little, and the sound is gone.

Also- advice directly from the HVAC install company owner: Buy the cheap filters, replace every month. Beats the HEPA stuff, even for allergens, and cuts down on "whooshing". It worked.

"Also- advice directly from the HVAC install company owner: Buy the cheap filters, replace every month."

That advice is so wrong I wouldn't believe anything else he said.

klem1, it works well- zero issues, noise gone. Apparently, the cheaper filters "suck" less, and so sure- you have to be disciplined about replacing.

Just put it through its paces- regular service, on their dime, according to their warranty- with an independent inspector, in accordance with my Builder's Warranty and it all passed with flying colors. So? I trust him, his 28 years in the business and the fact that he's on the hook for anything that happens for the life of the system.

Thanks, though, for your expert opinion. I assume you're an HVAC professional?

Yes,I have been around the block and cheap filters always clog coils. If you believe that feller will make repairs and clean your coils free for the life of the system ,you are dreaming. You mentioned "warranty",I'm betting you are paying for a service contract. It's your money to spend as you like,my advice is free. I've never talked to a technician that think's 3rd party warranties are worth buying,,,,,,,,,unless he's trying to sell one.

klem, I've checked my warranty, and it in no way specify what filters I should use. I'm not sure what neck of the woods you're from nor what junk you've run up against, but this isn't a warranty I paid for- it came with the system, and the installer is liable for execution. Yes- there are things that I have to do as a homeowner, specified as regular yearly service- that can be through any company certified with the HVAC manufacturer. I stay, right now, with the installer, because he has a lot to lose, should this fail in the next 10 years, and then still a bunch if problems occur after that- assuming I still own the home. "Feller" is a real, live business man who owns a large company with a great decades long reputation, both with his business and with the manufacture of my system. Don't think I didn't confirm both.

And all of this was negotiated and/or verified by a senior partner in a very large real estate firm, backed up by a Builder's Warranty, also legally drawn up by my attorney. None of it is something I pay for monthly. I know the difference between a service contract and a Warranty agreement. Do you? Maybe you have you never negotiated a whole contract, and just don't understand what people do to protect their assets. That's ok. I don't expect you to be able to play in all sandboxes- me, neither- but this is one you seem to really misunderstand.

Juanita, "cheap filter" doesnt really mean anything. Are you talking about fiberglass filters or a standard pleated filter (lower MERV)? I prefer the standard pleated filter as it still filters allergens but is not super restrictive on air flow. Otherwise, a 4" or 6" thick filter would be called for for both high filtration and airflow

In any case, that has nothing to do with it. The OP has one vent that is particularly loud. Sounds like a balancing issue, just needs an in-line damper to that one vent adjusted correctly.

Obviously, we dont have all the info so if her unit is oversized we wouldnt know that without looking at it all. Cannot assume it is oversized.

Fan speed can be adjusted as well depending on delta T.

juanita,I'm always happy to hear when consumers have good experiences with contractors. One of the main reasons people come here is looking for recommendations to good contractors. All that's left is for you to publish the name and location of your contractor. You will be doing the contractor and those people in his service area a real service. I do hope you will share,after all that's what houzz is about,sharing knowledge and ideas.

Anyone think she'll do that?