Sound proofing a vents in a research lab?
March 16, 2017 1:44 PM   Subscribe

I work in a research lab, and we've just moved into a new building (new to us and newly built). The HVAC in our testing rooms is pretty loud, specifically the airflow from the vents. We have two testing rooms, one with four vents and another smaller room with just one vent. Is there a way to sound proof around the vent area to reduce those noises?

There has already been some soundproofing to reduce general noises coming form the HVAC, but just the air flowing from the vent itself is producing a lot of noise in the rooms, especially in the room with four vents. We are doing studies that involving babies listening to sounds, so getting the sound right is important! Any advice from the hive mind on things we can do about this? Thanks!

I'll post videos of the vents/noise in the comments.
posted by ancient star to Technology (9 answers total)
Video 1
Video 2
posted by ancient star at 1:47 PM on March 16, 2017

You need to consult with institutional HVAC people surely, and not freelance this. The only real way to quiet an AC vent is to block airflow. The system may be balanced (building or zone wide) in ways that would be affected by doing this. It also likely entails adding insulating materials around the ductwork. Much of what you hear as sound originates elsewhere than at the vent. Anything on this scale that directly impeded the research function of a lab in a new or renovated campus building needs to get brought to the attention of your facilities/B&G people. I've been through wars over issues involving similar problems. Your chair needs to write a stern WTF email to the director of facilities or if the renovation is recent the project manager.

I have a weirdly deep knowledge of this subject. Get pros involved.
posted by spitbull at 2:35 PM on March 16, 2017 [7 favorites]

PS: It might end up being easier and more professional to create actual sound-proof enclosures if you're really measuring infant sound discriminations.
posted by spitbull at 2:40 PM on March 16, 2017

The vent that connects to the drop ceiling is called a diffuser, and some do exist that are designed for quiet, but I would not expect that to make a huge difference in itself (though it might be one piece of a multi-part fix.) The main thing that creates vent noise is trying to force a lot of air through a little space, so the surest way to reduce noise would be to 1) reduce the amount of air the HVAC system is pushing or 2) push that air through a larger opening or larger number of openings.

If these rooms have their own dedicated HVAC "zone" (i.e. if each room has its own dedicated thermostat or if there's a thermostat for these two rooms and nowhere else) it's possible that somebody could do something to simply attenuate the amount of air going to those vents (if there's no dedicated thermostat then the problem will require rebalancing of the other rooms being served by the system.) In this case the rooms would take longer to reach the setpoint temperature but should still be able to maintain it, barring terrible insulation or doors left open. Alternately, ductwork could be added to direct the output to additional vents, reducing the volume of air being forced through each individual vent.

On preview: I second spitbull's recommendation that this is something that should be handled as part of the facility's infrastructure, not something you try to end-run around in the room.
posted by contraption at 2:53 PM on March 16, 2017 [3 favorites]

I agree that you need to put this up the chain ASAP. Document the requirements that you have for the research space based on your current (and projected future studies). It sounds like the use of the space wasn't considered in the design and construction, but if you can state your requirements precisely (dB levels, etc.), even at this stage, you have a chance.
posted by demiurge at 3:45 PM on March 16, 2017

Generally, noise from air being supplied to a room is a result of too much air being pushed through too tight of a duct or register opening. The solutions are generally either to reduce the airflow or enlarge the opening it's going through, neither of which is something you can really do.

Also, I don't know what specific requirements your testing rooms have, if these are testing rooms in a lab there's at least a chance that the volume of airflow that you're getting is part of the design of the building, intended to create a positive pressure situation inside the room so that air from outside the room or air handling system does not intrude. That kind of thing is a requirement for "clean rooms" and food handling areas. It may or may not be applicable to your particular situation. Making it loud might even be part of the design as well, in a "do we know the system is working as intended" kind of way.
posted by LionIndex at 5:31 PM on March 16, 2017

Thanks everyone! This is such a long saga of new building/new space, and it has been very frustrating. Long story short, we had a space that was designed for us but had to give it to some other lab, and now we've just moved into this space, almost a year after everyone else has moved, because there were so many issues with the space originally. At this point, we're exhausted and disheartened.

No plans to hack something unless the facilities are super uncooperative. We just want to get a sense for our options so we know whether their solutions align with what should be done. Unfortunately, the HVAC system in place is an eco-friendly one that runs almost constantly. Our only access to changing the temperature is to adjust it a few degrees higher or lower. The fan is always running, so we can't turn that off.

We don't do any hard science work. Our "lab" consists of a booth with a TV in it, and some computer stations.

Our worst case-scenario is to get a sound booth, but those things cost SO MUCH MONEY.
posted by ancient star at 7:46 AM on March 17, 2017

Update: I took off the metal piece covering the vent on the low-hanging ceiling, and it's just a metal tube coming down to the ceiling, and the sound does not improve by taking the metal piece off (i.e. increasing opening for the air). I wonder if lining the duct with insulation would help with the sound?
posted by ancient star at 8:15 AM on March 17, 2017

Not likely. Sometimes wrapping the ducts on the outside with insulation helps because the airflow can cause the metal to vibrate at resonant frequencies. It's like a loudspeaker -- the point of emergence for the sound (a pressure wave in three dimensions) may be well behind the final duct opening and the entire structure is vibrating when air flows through it. You really need professional HVAC people to look at it because, as noted above, even taking a vent cover off or blocking it up can change the load on the zone or building and create problems system wide.

Many universities I know would cut a check for the soundproof booth to make this problem go away. HVAC troubleshooting gets expensive. A $5000 booth might be cheap at the price. The magic words are "interferes with our research."
posted by spitbull at 1:06 PM on March 17, 2017

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