How To Build A Vocal Booth (Part 2)
Jul 15, 2024In Part 1 of this vocal booth series I talked about different design options for your floor, walls and ceiling. In part two I will go over the best design options for your door, ventilation, and electrical/audio cabling designs.
1) Vocal Booth Door Options
When designing an soundproof room we have two options at our disposale. The first is to design a communicating door system where you have a door on each side of the wall with an air gap in the middle.
This is by far the best way to create a soundproof doorway. The basic principle is to design two heavy doors that are airtight. Now the details of building doors deserves it's own article and I have already taught extensively on how to build your doors here: https://www.soundproofyourstudio.com/blog/how-to-build-a-soundproof-door-part-2.
The main thing to consider when designing any doors is how heavy do they need to be. The best rule of thumb is to add up the mass of both of your walls and divide that between your two doors. For example, if you have two layers of drywall on each of your walls in a double wall system then your total wall weight is 8.8 Lb/sf. If you divide that in havle you get 4.4 LB/sf per door. Now if you have a 36x80" door you would multiply the 4.4 Lb/sf x 20 sf and get 88 Lb. That means each door needs to weight a minimum of 88 Lb and heavier is always better, although more expensive.
Now, vocal booths are inherently small spaces and having a communicating door may not be an option. In this case we need to design our single door to weigh as much as our two walls. In this case we would have to have a door that weighs a minimum of 176 Lb. Again, heavier is always better especially when we are dealing with one door and don't have the benefit of the sealed air gap between the doors.
So, you can see that designing your vocal booth will need to take into account the total mass of your walls and the amount of space you have for doors swings in deciding which door design you will use.
2) Ventilation
The best way to ventilate your vocal booth is using an inline fan, ducting and a baffle box system. The idea with a vocal booth is that it is far to small to need its own heating and cooling system, so instead we can run an air exchange system the the adjacent room that will transfer the conditioned air in that room into our vocal booth. Then we will have another fan and baffle box pulling the stale air out of the vocal booth.
Designing a ventilation system in such a small space is no small feat. My approach is to use quiet ventilation fans in combination with small baffle boxes that I can hide in the ceiling or outside the booth.
Here is the general system guidelines for your ventilation system.
A) figure out how much air you need. As a general rule each person in a room needs 15 CFM of air flow. CFM stands for cubic feet per minute and it is a very important number when designing HVAC systems.
For a vocal booth 15 CFM may be all you need so a small fan will work well. I personally, use the AC Finity A4 fans for all of my air exchange systems. This fan can go down to 15 CFM on the lowest setting and up to 165 CFM on the highest setting. This gives you a huge range of options when it comes to designing your baffle boxes.
B) Now that you know how much CFM of air flow you need, next we need to design our baffle boxes.
The baffle box is a system I build from plywood, duct board, and 5/8" drywall. It is simple in materials, but complex in design in the sense that you need to think carefully about how big to make your ducting in the box.
To do this I use a fancy calculator called a ductulator. Luckily, if you search google it is readily available for anyone to use. The basic idea with the ductulator is you want to input the air flow rate from your duct fans and the max air flow rate you want in the ducting. For our vocal booth I will have an air flow rate of 30CFM or less, but I am going to design my ducting with a max of 30 CFM. It's always good to overdesign so the air speed is even slower than needed.
Next, we need to decide our max air speed. The slower the max air speed the better. When air is moving slow we don't hear it. I shoot for 100 FPM (feet per minute) in my designs, but you can technically go up to 500 FPM and still fall in the range of acceptable air speeds for recording studio design.
Below is a screen shot of the ductulator and our example CPM and FPM numbers we talked about above.
Notice that we can have several options. We could use an 8" round duct or any of the rectangular ducts or even adjust the rectangular ducts to match a size that fits our design. To keep things simple, let's say we like the 8"x6" design. This means we want our duct size in side the baffle box to be 8x6".
So, how do you build the baffle box. Basically, I like to have at least one baffle, meaning a right angle turn in my baffle box designs. Below is an example of a baffle box from one of my clients studios.
Notice how I have two baffles in this design and the air flows around the baffles. The yellow stuff you see is what is known as duct board. Duct board is a just a fancy term for insulation board that is designed to be placed inside ventilation ducts. It helps with moisture control, sound absorption and won't irritate your lungs like typical fiberglass would. I like to use 2" of duct board, but I have used 1 1/2" as well and had success doing so.
To learn more about ventilation design I have a great youtube video here: https://youtu.be/slv9J_v1Gc8
3) Electrical and Audio Cabling
We have talked a lot about isolation building techniques, but what about power, lighting, and audio cables in your vocal booth. The best option I use is to buy a custom Redco wall plate and install in in the acoustic treatment of the vocal booth. I also would install one overhead light in the vocal booth in the acoustic ceiling treatment.
The key with any cabling through our soundproof system is to always keep our pentrations as small as possible. This means a single cable is always preferable to a full electrical box cut into the drywall. To do this I recommend installing all electrical boxes in the acoustic system of your vocal booth, not the isolation system.
When you penetrate your drywall cut a small hole for the wire or audio cable and use acoustic caulk to seal around it to ensure the penetration is air tight. Then you can install your j boxes for electrical outlets in the 2x4 acoustic wall, which I will talk about in Part 3 of this series.
The REDCO custom panels are great because you can put your power, audio cabling, HDMI, internet and many more connections all in one beautiful panel. This makes it easy to connect a single snake to the panel for your audio needs, a power outlet or two and an HDMI and internet cable to connect a spare computer, router or extra screen.
Conclusion:
As you can see properly building a vocal booth is no small task, but if you think through your door, ventilation and cabling designs carefully you will save yourself a lot of headaches in the future. Lastly, if you want some help and are not feeling the DIY method, reach out to me for a soundproof clarity call and I can help you design the perfect vocal booth the first time around.
Soundproof Clarity Call Application:
https://www.soundproofyourstudio.com/Step1
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