Vocal Booth Design
Disclaimer: I am not a carpenter, engineer, electrician, HVAC specialist, physicist, etc. The information on this website is provided to you free of charge, without any guarantee of desirable results. Treat this information only as a starting point; a rough-sketch of sorts. If you are unsure about any of the techniques used in the construction of this vocal booth you should seek the help of a professional carpenter, electrician, etc. By using any of my ideas as outlined below, you accept full responsibility for any loss, damage or harm that might befall you or others as a result.
DIY Vocal Booth Concept
My home recording space is primarily used for voice-over work. Doing voice-over or voice acting in a home-studio has two main drawbacks:
- Noisy recordings: Domestic noise such as household appliances and fighting children, or neighborhood noise like traffic and construction is guaranteed to ruin your perfect take.
- Disturbing others: To avoid these sources of noise, I often resorted to recording my voice overs late at night, when the house and neighborhood were relatively quiet. But a deep and dynamic voice booming through the house at 1:30am is generally met with disapproval. Subconsciously I would try to be quiet while voicing – even when the script clearly called for “energy” – to avoid disturbing the late night peace
The solution was to create a recording space with excellent sound damping properties. Notice I avoided using the term sound-proofing. A truly sound-proof space requires thousands of dollars, highly specialized materials, and degree of technical expertise – all of which I lack.
knew that my voicing career being held back because my recording space was just too noisy. It was a classic catch-22: I was missing out on voicing jobs because I couldn’t afford to upgrade my studio, and I couldn’t afford to upgrade because I was missing out on jobs.
The alternative to selling my kids on the black market to finance sound-proofing my entire studio space was to build an almost–sound-proof vocal booth.
First, my criteria; what were my objectives?
1) Size: the vocal booth couldn’t be too large – or it would eat into my recording space (which also happens to double as a home theater for family movie nights). But it had to be large enough for me to comfortably perform; I couldn’t worry about banging a wall or mic stand while voicing.
2) Comfort: after all, this is a work space where creativity and expression reign supreme. It had to reflect my personality and feel right; adequate lighting – but not harsh, a comfortable seat, a window to stave off claustrophobie, and ventilation to prevent death by hypoxia while working in an airtight chamber.
3) Acoustics: Above all else, the vocal booth must be quiet; the booth must prevent outside noise from bleeding into my recordings, and should also contain sound of my voice from spilling out into the room / living space and annoying others while I read the lines over and over and over and over. Not only did the vocal booth need to be relatively sound-proof, but it needed to sound neutral inside. Voicing in small, enclosed space can trigger sympathetic resonance of the walls, floor, and ceiling, adding undesirable peaks at certain frequencies.
4) Budget: The whole point of voicing is to make money – I know that sounds greedy, but lets face it; the family has to eat and I’d like to retire before I’m 85. A good voice and a home studio can be a source of extra income. It was ambitious, but I set a budget of $500. Keep in mind that my studio was already well equipped with some pretty decent gear – $500 was just for the booth.
Like Matt Damon’s character in The Martian, I was going to have to “science the shit out of this”.
Science of the Affordable Vocal Booth
I have decades of live and studio recording experience, so between me and my trusty side-kick Google, we were able to come up with a plan for a vocal booth that is both quiet and affordable.
Let’s start with some basic (yawn) physics…
- High frequency noise (birds chirping, little yappy dogs, telephones, etc) is made of low-energy sound waves which are fairly easy to eliminate – like little ripples on the surface of a pond that you can block with your hand.
- Low frequency noise (heavy footsteps, the rumble of traffic, booming construction) is made of high-energy sound waves and requires more effort to reduce – like rolling, crashing ocean waves that can flatten a beachfront house.
So, how do we eliminate unwanted sounds?
- Cancellation: Sound waves are cancelled when they meet a mirror image (inverse-phase) – this is called destructive interference. There are electronic devices that use cancellation to wipe out ambient noise, but this process introduces undesirable audio artifacts and degrades recording quality – so cancellation is not an ideal solution for noisy recordings.
- Reflection: Some materials possess high sonic reflectivity – these are usually hard, smooth, rigid surfaces, like concrete, stone, hardwood, and metal. These materials are unforgiving and don’t resonate, so the sound wave bounces (reflects) right off. This is very useful, especially for high frequency sounds – so reflection will be partly responsible for the sound damping of our vocal booth.
- Absorption: Some materials will absorb, rather than reflect sound – especially high frequency (low energy) sounds. These materials tend to be porous like styrofoam, which we will use for surface treatment to control reflection inside the vocal booth.
- Dissipation: Different materials reflect and/or absorb different frequencies. Building a wall with many layers of materials with different properties is an effective way of disrupting a broad spectrum of noise. This vocal booth will have many layers.
Okay, you can wake up now – physics 101 is over.
So, between reflection and absorption, I was successfully able to block a substantial amount of noise in the typical human range (20-20,000Hz). As I said from the beginning, it’s not 100% sound proof, but it is effective enough to block the types of noise that were causing 95% of my problems.
Building a DIY Vocal Booth
To reduce the costs and improve the overall effectiveness, I recommend placing the booth in basement if possible – where the room’s walls are made of concrete. If this is not possible, find a space in your home that is somewhat isolated – away from furnaces, laundry appliances, water pumps, etc. – and choose a corner where the walls are most dense; probably the exterior walls of your home.
Prices of building materials fluctuate between seasons and regions, so I won’t publish many costs. Suffice to say, I did my homework and selected the best materials for the job within my $500 budget.
I like to buy a little extra of everything and return what I don’t use. It’s easier than running short when you’re in the middle of a build.
- 2×4 studs. Usually sold in 8-ft lengths and milled to 1-1/2″ x 3-1/2″. You’ll need at least 18, but buy 20 just to be safe.
- High-grade pine boards (NOT “knotty pine”). Sold in 8ft lengths. 6″ x 3/4″. Buy 6 of these.
- Pine baseboard. Plain, flat, no curves or scrolls. 8′ x 3″. 12 of these
- ALTERNATIVELY, you can save a lot of cash and make your own trim by ripping 2×4’s lengthwise. It’s good way to lose a finger/hand/eye so be careful if you choose this route.
- Laminate flooring. 20 sq.ft.
- Drywall, 5/8″ thickness (gypsum board). 4′ x 8′ sheet. 3 of these.
- OSB (oriented strand board), 3/4″ thick. 4′ x 8′ sheet. 4 of these
- Spruce ply-wood. 1/2″ thick. 4′ x 8′ sheet. Just one.
- MDF, 1/2″ thick. 2′ x 2′ sheet. Just one
- Glass. 1/4″ thick. 22″ x 8″. 2 of these.
- Acoustic sealant/vapour barrier adhesive. 300ml tube. 2 of these.
- Construction adhesive. 300ml tube. 4 of these.
- Clear window caulking. 300ml tube. Just one.
- Spray foam expanding insulation. 454g can.
- Closed cell, rubberized foam tape (weather stripping). 1/2″ wide, 1/4″ think. 100-ft roll.
- 4″ wood screws. 1/4-lb
- 3″ wood screws. 1/2-lb
- 2-1/4″ wood screws. 1-lb
- Drywall screws. 1/4-lb
- finish nails. 1/4-lb
- Door hinges. 2
- Vent covers. min 4″ x 10″. 2 of these.
- Magnetic cabinet latch. 4 of these.
- Light switches. 2
- 2 switch cover plate. 1
- Two gang switch box. 1
- 80mm, 12VDC, QUIET computer fans. 4 of these
- Surface mount 12VDC LED light strips (8 – 12 inches long). 2 of these.
- Acoustic wedge foam, 1-inch thick. 12″ x 12″. 48 of these
NOTES about Materials:
- The acoustic sealant is EXTREMELY MESSY to work with. I’m not 100% convinced that it’s effective when used as we’re using it – If I was to do this over again, I would consider replacing it with construction adhesive.
- Consult your local electrical code regarding the use of 12VDC lights and fans. If you’re not familiar with electrical, consider hiring an electrician.
- Speaking of cheap … I bought locally where I could, but some things were only available on-line, and some other things were just too expensive to buy locally.
- Of note: I bought the 12VDC fans on ebay. They came from China and cost $1.50 each including shipping.
- I shopped the world and found the best deal on acoustic foam at The Foam Factory: http://www.thefoamfactory.com/acousticfoam/wedgefoam.html
- Recycle or Up-cycle where possible. I scavenged the LED panel from a discarded laptop and used it as a surface mount ceiling light.
- NOTE: The measurements in the diagrams below are rough/rounded – i.e. not exact, so don’t use them. Every room is different – so do your own measurements to meet your needs.
- Start by building the false floor out of 2×4 studs (1-1/2″x3-1/3″) – See the image below – Screw it together with 3″ wood screws. This will be the foundation of the vocal booth. Everything else is built on top of this. There cannot be any squeaks or movement in this floor, so don’t be stingy with the screws. A little glue wouldn’t hurt.
- From the leftover ends of 2×4’s, build maze* for ventilation. (*maze: the theory is that the twists and turns of the maze will disrupt the noise of the vent-fan, but will allow the air to pass)
- Using a hole-saw, drill a 2.5″ round hole in the side of the floor frame 3″ from the right corner. You will be attaching a fan-box here in the final steps.
- Apply rubberized closed cell foam tape (weather strip) to the underside of the entire floor frame. This will reduce foot noise when stepping on the subfloor, and help to level out any flaws in room’s structural floor to prevent wobbling. It will also improve airflow through the maze by creating a seal between the sub-floor and structural floor.
- Cut a sheet of 3/4″ OSB exactly to size. Apply a bead of acoustic sealant compound to the entire top surface of the frame. Align the OSB with the frame and screw into place with 1-3/4″ wood screws. We don’t want this floor to squeak or creak, so be generous with those screws!
- The left (short) wall is a simple rectangle. Mine is 30″ wide, but measure yours to suite your space. Measure so it extends from the surface of the subfloor up to the ceiling.
- Likewise, the door frame is a simple rectangle, approximately 26″ wide, with a header 6″ from the top. (NOTE: This 26″ wide door-frame will allow for only a 19″ door after we build a sound-seal. If you need a wider door, adjust your measurements accordingly)
- The right wall has 9″ x 23″ opening for a window, and another air-way maze – similar to the subfloor.
- Cut 3/4″ OSB sheathing to exactly match the left wall-frame.
- Do the same for the right wall frame, cutting out the window opening as well.
- Cut 1″ Polystyrene Foam Insulation to match the left and right frames.
- Apply a criss-cross bead of construction acoustic sealant to the exterior side of the OSB sheathing.
- Carefully align and press the press the polystyrene foam onto the OSB.
- Apply a single bead of acoustic sealant to the surface of each frame, and press the joined OSB/Polystyrene onto it.
- Align exactly and screw the OSB/Foam into place with minimal* number of 2-1/4″ screws. (*screws provide a medium for sound vibrations to travel through the wall, so use as few as possible – one in each corner and another every 24-inches)
- Using 3″ screws, secure the left wall, right-wall, and door-frames to the subfloor
- Once all three sides are secure, plumb and true, fasten the door frame to the side walls with 4″ screws.
- Lastly, measure and cut two strips of OSB to finish the inner side of the door frame opening. Cut a piece to close the header gap above the door opening.
- Cut three pieces of polystyrene; same size as the OSB you just cut.
- Laminate the OSB/Polystyrene to the door frame with acoustic sealant and 2-1/4″ screws
- Fill the wall cavities of the left/right walls with Roxol Safe-n-Sound insulation (DO NOT fill the air-way in the right-wall).
- Drill 2-1/2″ holes for airflow
- through the studs that separate the lower, middle, and upper chambers of the air-maze.
- in the upper chamber through the OSB/polystyrene inner wall
- at the bottom of the lower chamber through the gypsum board.
- through the gypsum board where the air-hole was drilled into the sub-floor
- Mount a 2-gang electrical box (for switches) below and to the left of the window.
- Run 12VDC supply line up into the ceiling for lights
- Run two lines down to the fan-box location in the lower right exterior corner – one will be the feed from power supply to the switch box, the other will provide power to the fans when the switch is in the ON position.
- This is the ideal time to run any other cables (Microphone or two, video monitor, headphones, cat5e, etc) into the booth – while the wall is open and accessible.
- Apply a bead of acoustic sealant to the exterior face of the wall/door-frame studs.
- Measure gypsum board to fit and secure to studs with minimal screws.
- It’s a good idea to leave a 1″ or greater gap between the bottom of the gypsum board and the floor – After you install the baseboard, this gap will be great for hiding speaker-wires and such.
- Your vocal booth will have a false ceiling. 6″ below your structural ceiling, secure a course of strapping along all walls, including above the door and on the existing corner walls.
- Also, use two pieces of strapping to span the width of the booth
- Fill the 6″ space between the strapping and the structural ceiling with a double layer of sound-proof insulation (I recommend Roxul Safe-n-Sound).
- Cut a sheet of OSB to fit for the booth ceiling.
- Cut an identical piece of Polystyrene.
- Bond them together with acoustic sealant.
- Drill 1/4″ holes and pull the wiring for the lights down through, before fastening OSB/foam to the underside of the strapping with 3″ screws
The Door Casing
- The overall thickness of the door casing should be 5-7/8″ (5/8″ drywall + 3-1/2″ stud + 1″ Polystyrene + 3/4″ OSB)
- So, it’s best to start out with solid pine, 6″ wide x 3/4″ thick. Rip this to 5-7/8″ wide. Use this for the door casing: Unlike most door casings, this one will have a top, sides, and bottom/sill
- As you put this together you might notice a 2-3/8″ gap under the sill – this is because the door frame studs are only 3-1/2″ and the casing is 57/8″. Stepping on this will eventually cause the pine casing to split, so cut a leftover piece of stud to permanently slide in under the sill for support.
- Once the pine casing is secured to the studs, measure the width and height of the opening. Subtract 1/4″ from both measurements – these are the dimensions of the actual door.
- Write down the dimensions of the door as determined in the previous step – you’ve got some math to do…
- First, cut two 2×4 studs to the appropriate height – these are the left and right edges of the door.
- Next, rip a groove down the center of a one wide edge – one groove per stud.
- The groove should be 1/2″ deep x 3/4″ wide.
- Now, assuming your studs are 1-1/2″ thick, subtract 3″ from the width of the door (the width, as you have written down) – and cut two of these from a 2×4. These are the top and bottom edges of the door.
- Rip a groove down the center of these as well – one side on each.
- Subtract 2″ from the width and height as you have written down and cut a sheet of 3/4″ spruce plywood to these dimensions – this is the door panel.
- This rectangular plywood panel should fit snugly into the grooves along the top, bottom, left, and right door edges. DON’T screw/glue anything together yet… Check that everything is square and that the finished dimensions are exactly as you have written down. If anything is off, now is the time to correct it.
- If it’s all good, disassemble – proceed by running a thin bead of construction adhesive in the four grooves. Reassemble, checking again for correct dimensions and right angles. Secure the four corners with 3″ wood screws.
- The panel, on both the front and the back, will be inset by 1-3/8″.
- Measure the width/height of the inset front panel and cut polystyrene foam to fit.
- Cut gypsum board to the same dimensions.
- Bond the polystyrene and gypsum board with acoustic sealant.
- Apply sealant to the surface of the front door panel. Press the polystyrene/gypsum board into place and secure with minimal 2″ drywall screws.
- Repeat for the back panel.
- The door can now be hung in the casing on hinges – position it flush with the exterior and swing outward.
The Door (Part 2)
- Once the door is hung, plane any sticky edges to minimum tolerance – try not to exceed 1/8″ gap on any side.
- Once planed and freely opening/closing without obstruction, apply closed-cell rubberized foam tape (weather strip) to the inside face of the door, as close to the edge as possible.
- Then, with the door closed flush, mark the position of door stops on the casing around all four edges.
- Install door stops – I ripped a 2×4 down to 1″x1″ for these – when the door closes, the foam tape should now rest snug against the stops. There should be no air gaps, nor should the tape be so compressed that the door “pops” open.
- There is fine line here – it took me several attempts to find the sweet spot.
- Now, last step … using 3″ wide x 1/4″ solid wood trim (DON’T use MDF for this, it will warp) – measure, cut and fasten the wood trim to the front face of the door so there is a 1″ overlap all the way round.
- Apply a strip of closed-cell foam tape to this overlap, so when the door closes the foam tape creates a seal around the door.
- Again, there should be no air gaps, but it should be bulky enough to prevent the door from staying closed.
- NOTE: depending on your level of precision – or lack thereof, in my case – you might have to use two strips of foam-tape, one on each of the facing surfaces, to achieve a good seal … it will no doubt require some fussing/trial-and-error.
- Finally, with the door held closed, position and mount the magnetic catches. The door should now effortlessly “click” closed, held only by magnets, and have an airtight double-seal all the way round.
- OH MY GOD – YOU’RE TRAPPED! – 1/2 an hour ago would have been a good time to fashion a door handle from some scrap wood.
- Just like the door casing, the window is also 5-7/8″ deep and made of 3/4″ pine.
- Measure the width and height of the window opening – 23″ x 9″ in this example – these are outer dimensions of your window. It has to be a very tight fit, so there is no need to allow for a gap.
- The dimensions of the glass panes will be exactly 1″ shorter and narrower than the outer dimensions – so, 22″ x 8″ for this example.
- Give these measurments to your local glass shop – Ask for 1/4″ glass, like they use for glass shelves. (My local shop – Sam’s Auto Glass in North Sydney – charged $20 for both panes)
- Using the outer measurements, cut four pieces of pine – the top, bottom, left and right sides.
- Rip two grooves, 1″ apart on center, 1/4″ deep and 1/4″ wide, along the length of one of the longer pieces.
- In the other long piece, rip two grooves 3″ apart on center, 1/4″ deep and 1/4″ wide.
- Clamp everything together and mark the spots where the four grooves in the long pieces intersect with the short pieces – four spots on the end of each piece.
- Connect the dots as if you were making a “V” with a flat bottom on each short piece.
- Remove from the clamps and rip grooves along these lines as well.
- Clamp together one long and two short pieces.
- Slide the two panes of glass all the way down into the “V” grooves – check to be sure the glass sits in the grooves of the long side. Join the 4th side and confirm that everything fits – you might have to widen the grooves by a 1/16″ because of the angle of glass.
- MEASURE AGAIN to MAKE SURE the finished assembly will fit in the window opening.
- I made the mistake of putting clear caulking in the grooves – DO NOT DO THIS.
- If it all fits – screw it together at the corners (drill pilot holes first to avoid splitting the wood), and slide the completed window into the window opening.
- You can now put clear caulking around the outer edges where the panes meet the pine frame.
The Fan Box
- 1/2″ MDF is ideal for this.
- Front and back pieces are both 8″ x 12″.
- The two sides are 3″ x 12″
- The top, bottom and divider are all 7″ x 3″
- The fan box will rest on the floor, so drill two 2-1/2″ holes in the back panel of the box, in exactly the same positions as the two air-holes on the booth (lower right corner of right wall). The holes in the back of the box have to line-up with the holes in the booth.
- Drill four 3″ holes in the front panel of the box – two across the middle of the upper half, two in the lower half.
- Drill a 1/4″ hole in the bottom center of the left panel.
- Drill a 1/4″ hole in the center of the divider.
- Assemble the box as shown in the diagram, using the divider to separate the upper and lower halves of the box.
- Run the 12VDC line form the switch box in through the 1/4″ hole in the side of the fan box.
- marette or solder four leads here (parallel) – one for each fan.
- Pull two leads out through the bottom fan holes.
- Pull two leads up through the divider and out through the two top fan holes.
- Secure the box to the outside of the booth with construction adhesive (NOT screws) so the air holes line up.
- Connect the 12VDC to fans and mount the fans over the four holes –
- Orient the top two fans to blow air OUT of the box
- Reverse the the orientation of the bottom two so they blow air IN to the box.
- Check the output of the power supply that came with your LED lights.
- Measure the load for the four fans and two lights combined. Make sure this load doesn’t exceed the max of the power supply. If it does, you’ll need to source a power supply with more available current.
- Assuming you have enough juice, connect the 12VDC power supply to the lead coming down from the switch box.
- Might as well connect the switches now, while you’re at it, because the lights are next …
Inside the Booth
- Connect and mount the two LED light strips to the ceiling.
- Lay the laminate floor as per the instructions on the box.
- Drill two 2-1/2″ holes, side by side, through the floor into the air chamber at the end of the maze in the subfloor frame.
- Finish trim as needed around the window, door, and in the corners.
- OPTIONAL: Instead of using the pre-milled trim, I ripped a couple of 2×4’s and made my own 1-1/2″ trim.
- Apply the acoustic foam tiles to the ceiling, inside of door, sides, and back of booth
- You only have 48 sq.ft. so you’ll need to figure out how many squares go in each location.
- Build a script stand from of leftover wood. Mount it permanently to the front wall so it doesn’t vibrate or rattle.
- Finally … FINALLY … give it all a coat of paint and crack the Dom Perignon because YOU … ARE … DONE !!!
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If you haven’t watched the VIDEO, you should – it has some helpful tips.