How to ventilate a soundproof room or booth?
I have lost count of the number of soundproofing projects that I have personally undertaken, as well as a few that I helped my friends with.
Interestingly, the projects usually occur in larger spaces, but there were a few where I soundproofed a small basement as well as one for a recording booth or studio. That was when I realized that ventilation is a really important aspect of the entire project, and hence I decided to share what I know.
If you wish to learn how to ventilate a soundproof room or booth, this article could just be the right help you need.
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Why are room vents loud?
It is normal for your air vents to make some noise when the system fan is turned on.
It goes for all the air vents connected to your heating and air conditioning duct (HVAC) system which includes return grilles, floor vents, supply registers and ceiling diffusers.
Yours can be louder than others due to a couple of reasons that we will discuss ahead.
First of all, you should know that it is most probably the air moving through your ducts and not the ducts themselves that make noise.
Some underlying factors make it less or more audible to you.
So, I’ll start with the most common issue that causes noise- air restriction. After that, we will address two other possible reasons.
1. Air flow restriction
When the flow of air is restricted, your duct system will have to draw in more air. This causes the pressure to increase and hence, sound level enhances. It can be due to:
- Closed duct dampers:
To ensure proper flow of air, always keep all of the dampers on your ductwork system open. Closing of even one can affect the air flow through the whole system.
- Junk accumulation in ducts:
If you are hearing a rattling sound, then it’s most probably because your duct has accumulated junk in it. It can be sawdust, screws, nails or anything else. If you are unable to access the duct, you need to call a professional for cleaning.
- Obstructed vents:
Free your vents from all kinds of obstructions like furniture, window coverings or rugs. This is to let air pass through them freely.
- Dirty air filter:
Keep a check on your air filter. You can do it monthly. If you find it being clogged with debris, replace it.
2. A faulty duct system
Yes, you heard it right, duct systems can be faulty. This kind of duct system can also be an underlying cause of noise. Following are the possible defects:
Ducts come in three different shapes – round, square and rectangular. The round ones are the the quietest while the rectangular ones are the loudest. This is something which depends solely on your choice. So, the next time you buy, go for round shaped ducts.
If the size of your ducts is not in sync with the size of your house, they are going to have problem meeting your requirements. It will make them contract and expand more often, making a popping sound.
- Gauge rating:
All metals have a gauge rating. The one used in your duct also have one. The lower is the gauge rating, the quieter the metal is. This is because lower gauge rating means that the metal is thicker and stronger. So, get that checked too.
3. High static pressure
When your ducts are unable to accommodate the volume of air pushed out by your equipment, it leads to high static pressure. It doesn’t make any sound itself but makes every sound more audible, which is a problem. To check, consult a professional.
Solutions can be:
– Lowering your fan speed if it is too high. Don’t interfere with it unnecessarily if it is properly set up, otherwise you may end up worsening the situation.
– Adding more ducts if the existing ones are too small.
– Expanding the size of your grilles.
– Installing a bypass duct in the system.
If you solve all of the above issues but see no results, consult a professional HVAC expert. He will check the CFM (Cubic Feet per Minute) of air movement through your system and do something about it.
This is all you need to know before proceeding with the real DIY ventilation work.
(Tip: Use flex ducts instead of hard pipe ducts. They may be prone to bends and kinks but are quieter as well.)
Ways to ventilate a soundproof room or a recording booth
In my view, it is better to ventilate a soundproof room or recording studio than to soundproof a ventilation system. You can check out how to soundproof air vents here if that is more suitable for your situation.
Because it’s easier to let in air than to prevent leaking of sound or coming in of sound. So, without further ado, let’s get started.
I will be showing your four methods:
- Building a maze box
- Soffit mufflers
- Building a vent baffle
- Building a dead vent
1. Building a maze box
Step 1: Figure out your source of air
Look around and decide what is the best air source around your recording studio. It can be a window of your basement or something else that can provide you fresh air.
You are going to use ducts to connect that source with your room.
Step 2: Get some in-line duct fans
They can cost you less than $50 per piece. You need them for a constant flow of air in your room. It doesn’t mean that you’ve to always keep them on.
In some cases, you won’t need them at all. But it mostly depends from place to place. So, be sure to buy them and have them ready.
Step 3: Construct a wooden maze box
Now, craft up a small maze box, just about the size which can accommodate the duct twice over. Twice because we will turn the duct 180 degrees for better sound absorption.
If you’ve only one duct, then instead of craving a hole in your maze (which can sometimes mess up if not craved out properly and can leak sound), leave the bottom uninstalled.
This way, any sound that will try to leave or enter your room via duct will be absorbed.
Step 4: Set up the ducts
Pick up the ducts and lay them out as planned. Starting from the air source and then moving towards the studio.
You can keep setting up in-line fan for later if you wish to.
Step 5: Piece everything together
Finally, you have to close your maze box. But before that, take some Rockwool and fill it in, as much as you can. Try not to leave any space for air.
At last, close it with a drywall lid and seal it wherever you want to. It would be better on the ceiling if you are looking up to spare some space.
For some similar options, you can consider using Soffit mufflers (ventilation mufflers) or building a dead vent. There’s not much difference other than the fact that dead vents can fit in walls and under floor.
2. Soffit mufflers
Soffit is the extra ceiling in form of arches or balconies. You can call it a false ceiling or a wall cavity. See the image below. A soffit muffler will dampen all the sound coming through your ventilation system before it reaches you.
Follow these steps to build your own soffit muffler:
- Lay out your flex duct, starting from the vent and then to the HVAC system.
- Construct a box under the soffit made up of double layer drywall held together with the help of Green Glue.
- Install a HVAC silencer inside the box and fill it with Rockwool insulation.
Make sure that this box covers as much portion of the flex vent as possible. Also, apply enough glue to keep away rattling noises.
And with this, you’re done!
3. Building a vent baffle
A vent baffle can be combined with your HVAC system. It takes up really very little space so it can be ideal for a small house. They are typically used in conjunction with soffit to channel air flow to the attic, but it can be repurposed to use as ventilation too.
Steps to follow:
- Use MDF board to construct a box having a measurement of 2’×1′.
- Now, we have to install a duct fan in it. So, create a mount for the fan in the middle of the box.
- Cut out two holes from the shorter sides of the box, opposite to each other.
- Insert the flex duct from one end and aim for bending it by 90° at least 4 times, before taking it out from the other end.These turns are meant for scattering away the sound waves.
- Finally, fit it into your HVAC system and use weather stripping to seal the gaps.
Your vent baffle is ready!
4. Building a dead vent
A dead vent can fit in with your HVAC system under the floors or in walls. Though, I would suggest not to do that if you need proper sound insulation. Its main principle is dead air space. It will let the sound enter, trap it and let it out where it cannot be heard.
For better results, consider creating a dead vent for both input and output vents.
- Construct a box of double layered drywall held together by Green Glue. It should measure about 96″×24″.
- Cut out a hole having 6 inch diameter on each of the longer sides on the opposite ends. This is because we are going to lay down the duct in a S-shape.
- Now build a bracket for fan that will be fixed in the middle of the box.
- Add insulation pads around the fan to dampen its noise.
- Turn on the power for a while to check if the box is functional or not.
- Fill up the box with Rockwool insulation but do not stuff very hard.
It is now ready to be installed in your recording studio.
Frequently Asked Questions (FAQ)
Does a soundproof room need a vent?
Of course, it does, especially smaller ones and those that do not have air conditioning. Depriving yourself of fresh air in your recording studio or a sealed room doesn’t sound like a good idea to me. There are methods to keep the sound out/in while letting the air in, so why not try them out?
Does sound travel through air vents?
As the name suggests, air vents are air passages. Sound waves travel through air. So, yes, sound does travel through air vents. You can easily hear sounds from neighbouring room or of wind. But that doesn’t mean you have to let it be. You have options like Soffit mufflers to use.
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