Building A Home Studio: SOUND INSULATION
So, you’re actually building a home studio! Pretty exciting. You’re wondering what to do about sound insulation. In the big picture, sound insulation is just one component in creating a sonically discreet space. You’ll want it to be as quiet as possible. The goal is to get the lowest possible noisefloor you can in your home studio.
What is a Noisefloor?
A noisefloor as the amount of ambient sound in your space when no one is speaking or moving. The professional studio standard noisefloor is about -55 to -60 decibels (dB). If you can get anywhere near that, you’re doing extremely well. Most home studios don’t get below -40dB.
I have an app called Sound Meter on my phone. This snapshot here reflects the noise level in my living room with the windows closed and the HVAC off. Why is it 19.6 and not 0 db? Because things in our living space generate noise. Noise that we no longer notice because our brains have moved it from the forefront of our perception and tagged it as background. Stuff like refrigerator compressors, computers, ceiling fans and who knows what else. We don’t realize at first that it takes some work to build a quiet space. Especially if we live in the city with sirens, helicopters, lawn mowers, cars blasting bass music or kids and pets. The goal for our home studio is to build a very quiet, acoustically dead room.
A Live Room vs. a Dead Room
A “live room” has a lot of hard surfaces with bare walls, hardwood floors, countertops, video screens and mirrors, which reflect sound waves and cause them to bounce from floor-to-ceiling-to-wall, etc. creating an echoing, cavernous sound. In recordings, you can “hear the room” and that’s bad.
A “dead room” like a recording booth or even a home theater, has a lot of soft surfaces like couches, people, curtains, rugs and in our case, sound insulation (foam). These surfaces absorb sound and keep it from bouncing. Sound waves hit the absorbent surfaces and stop. No bounce. Creating what we call a dead room. And that is good for recording or listening to audio.
To test a space, clap your hands. If you hear a lot of reverberation, it’s too live. Insulate until the clap gets eaten by the foam and there’s no bounce. No echo. No sense of “hearing the room.”
Professional commercial studios hire acoustic engineers to design control rooms and recording booths for optimum conditions. These experts go beyond live and dead. They often combine hard and soft materials to create a natural sound- mostly dead, but with just the right amount of live.
When it comes to the human ear, natural and optimum are, of course, subjective. Everyone has an opinion and all professional studios sound a little different. For our purposes, we’ll deal exclusively with how to deaden your space, since most homes already have so many inherent live qualities.
Before we go there, I should tell you that if you have the money and you’re building a serious career, you can spring for a professionally-designed portable sound booth. StudioBricks, Demvox, Port-a-Booth and WhisperRoom are some of the top names in pre-fabricated sound booths. They cost $5000-$20,000, depending on size and features. Some are egg shaped; most are actual rectangles. They build them and ship them to you, some assembly required.
“Dr. Who to the sound booth. Dr. Who...”
Some even come pre-wired, have ports for HVAC and just like an Escalade, cup holders! Great stuff if you can afford it. If you’re on a limited budget, most pre-fab sound booths are probably beyond your reach. Besides, you get one and then you have to answer to the Timelords. So, let’s look at more affordable options.
Walk-in Closets
The next best thing to a pro booth is a converted walk-in closet. Think about it; it’s already shaped like a booth. If it’s filled with clothes, that will take care of most, not all, of the sound insulation needed.
If it’s a big closet with clothes hanging on either side, you can set up in the middle and all you have to worry about is deadening hard surfaces, the ceiling, the front wall and the door behind you. A lot of VO people put a desk in there. That takes up a lot of space and I prefer to stand when I perform.
If it’s a smaller closet, you may have to empty it out and place acoustic insulation on the walls and ceiling. Some folks hang blankets. Whatever defeats the bounce of sound waves. Probably no room for a desk or workstation. Standing is better anyway, trust me. Sitting cuts the instrument off at the bottom; tilting your head down to read a screen that’s mounted too low, cuts it off at the top.
If you have a big, bad gaming computer with spinning hard drives and several fans, move it outside the actual recording space. You’ll need some long cables. Also, using a wireless mouse and keyboard to control the recording software from inside the booth is super convenient. If you have a modern Solid State Drive (SSD) laptop you should be OK. New generation Macbooks and Airs are almost silent when operating.
Using a Bedroom or Home Office
OK, so you don’t have a closet. Or your significant other says, “My shoes need a place to live and this closet is it. Keep moving. Nothing to see here.” So, you slink off to your bedroom or home office, form an image of your dream studio in your mind and start measuring walls.
Some acoustic engineers say it’s not important to insulate a wall closer than 3 feet from the floor. That might be true for recording a band. For VO, I insulate the entire wall, floor to ceiling. I built the Voices Carey Studio in Dallas with the help of an electrical engineer. I played the part of acoustic engineer, drill operator and wire worm. Based on experience, I want the insulation to stop at the floor, not my knees.
So, you can insulate the entire space or a portion of the space. If you deaden the entire room, it can get expensive. Also, is it necessary? A large space is still a large space, and harder to control. That’s why booths are smaller. The acoustics are more manageable, physically and financially. A corner can work. You put the mic in the corner and insulate the walls 6’ or 8’ back, on 45 degree angles from the center. Do the ceiling too. I hope you have carpet or a rug on the floor.
Square Angles Are Not Your Friend
Of all the math courses I’ve taken, geometry was my favorite, because examples are everywhere you look in real life. From Grandma’s cherry pie- a circle cut into wedges- to the 90 degree angle of two walls meeting. For sonic isolation, curved surfaces are better than sharp, square angles. Square corners facilitate sound wave transmission. Bounce. Like a bank shot on a pool table, except in 3D. When I insulate a corner, I put the center of a foam sheet directly over the corner; I don’t cut it so the two pieces meet the corner perfectly. I leave it curved. I like the curve. It works better and sounds better. After all, that’s the mission here.
Using Your Existing Workstation
Build a PVC framework around your current desk or computer workstation, then mount acoustic insulation on the frame. Also, you can insulate those 3 section standing room dividers and place them around and behind you. I’ve seen some actors get pretty creative. Whatever works.
Foam Sound Insulation
So now, we’re down to it: acoustic insulation. Remember, our goal is to deaden a live room by turning hard, reflective surfaces into soft, absorbent ones.
Foam comes in myriad shapes, patterns, colors and thickness. Patterns like wave, pyramid, grid, eggcrate, spade. Thickness from 1” to 4”. Colors? Taste the rainbow. Cost varies widely depending on how you design your space and what materials you choose.
Each type of insulation has a different Noise Reduction Coefficient (NRC) and a different Sound Transmission Class (STC). These ratings are used to compare the acoustic isolation of different materials. I wouldn't worry too much about that unless you are a professional acoustic designer, which I'm guessing you're not if you're building your first home studio. They all work and most people just buy the pattern and color they find appealing. I like the purple wedge. Not the purple dinosaur. That I Love You song drove me crazy.
If you buy the best 1x1’ acoustic tiles for $8-$10 a square foot, doing an 8x8’ wall will cost you $512. And that’s just one wall. A much more cost effective way is buying sheets, rather than tiles. The cheapest, but still effective way to go is 1 ½ “ eggcrate. A 72" x 80" x 1 ½ “ sheet of eggcrate acoustic foam is $33 from TheFoamFactory.com. A little easier on the wallet, I think you’ll agree.
The thicker the insulation is, the more effective and expensive it is. If your budget is tight, get the charcoal 1 ½ “ eggcrate. If you can afford it, buy the 3” wedge or pyramid in electric purple or fluorescent green. That thickness will really do the job.
Something else to consider is space, especially if you’re claustrophobic. Putting 3” insulation on the walls and ceiling makes the recording space 6” narrower and 3” shorter. “Dad, let me out! I’ll be good, I promise!”
When mounting the foam sheets, use pins or heavy duty Velcro. Or both. That spray adhesive is nasty on the eyes and lungs.
If you have a big, boomy voice, you may want to invest in bass baffles. They are 3ft high, 8-12” deep triangular foam wedges you stick in the corners. You can stack several on top of each other to bring them up to mouth level. They’re very effective in eating up those excessive low frequencies, if you’re a baritone. They also eat up a lot of space.
Other Types of Foam That Will Work
Lately, people are ordering mattress toppers and mounting them on the walls. Here’s a cool one that incorporates 5 different patterns in one 2 ½ “ thick sheet. At the end of the day, it’s foam. It works. I don’t recommend gel mattress toppers. They’re heavy and hard to keep mounted.
There are also various brands of sound shields that stand behind the microphone, stopping a good portion of sound waves from going too live. A lot of performers use them and they do help quite a bit. Just remember, this is only one ingredient in creating your sonically discreet dish, not the whole enchilada.
Summary
It takes planning and work to create a good-sounding, acoustically desirable room. You can spend a little or spend a lot. Achieving the goal is the main thing. If your space is big enough, don’t mount the foam sheets flat against the wall. Leave some slack and let them bulge in waves, convex and concave, billowing slightly down the length of at least one wall. Straight angle to straight angle, even insulated, can still be live. Straight angle to curved surface- not so much. I’ve had really good luck with this technique of not designing straight-angled rooms over the years.
We’re all trying to get the most bang for our buck. In the end, sound quality is a subjective thing. The space is yours and it has to please you. Even once you get set up, you will be making constant adjustments until you like how it hits your ear. And other factors, like the microphone and audio interface you’re using contribute heavily to the overall finished sound of your studio. You can create a really good home studio without it costing an arm and a leg. Give it some thought, spend wisely and you’ll get there.
Coming up: Building a Home Studio: Headphones
