Increasing STC rating without increasing depth? (building a portable vocal booth)

KJI

New member
Okay, here's my predicament:

I'm a college student who lives in a apartment complex with pretty thin walls. I'm also a home recordist (vocalist) who hasn't really had a chance to practice or record in the last year since moving out of my parents' house. It's killing me.

I've been toying with the idea of building a portable vocal booth for a while, and actually decided to google it a few months ago. I found this site and explored it a bit, but decided to wait until around the holidays to further investigate. I just recently got the chance to do a bit of research via google, this forum, and other various sites, so I now have most of the plans of what I want down.

1. Dimensions: I want my booth to be about 3.7'x3.1'x6.5'. I'm 5'10" myself, I've read enough to know not to make the dimensions multiples of each other, and the smaller it is the more portable it gets. However, I've read that too small and it starts to get boxy in addition to getting more cramped. Thus I think this would probably be the best size combo out of all.

2. Isolation: I don't really need to isolate sound (which would be impossible anyway), just decrease it enough. The end result is that I want it to not (or barely) be heard outside of my room. For example, if I scream inside the booth, it'll sound like low talking outside the booth, and maybe a murmur outside my room.

3. Design/materials: Portability is the key word for me. For one, I have to build it at home, then transport it 60+ miles to my apartment in/on my father's station wagon. I also plan keep it disassembled against a wall or something when not in use, and only set it up during weekends. Also, I might decide to take to friends houses or back home during holidays. Because of this I plan to have the panels lock together via metal clasps when in use, but they can be unlocked from one another when not in use.


As I said before, I was originally planning to follow the general plan from this site, but after reading different threads in this forum I found pandamonk's plans in this thread, which was more like I was considering using anyway. However, this is where my problem starts.

Just the 2x4 timber alone decreases portability (weight+depth), not even mentioning the fiberglass. The end result, although being incredibly superior than the first at blocking sound, wouldn't be as portable and easy to store.

Thus, it appears I won't really be able to take advantage of the mass-spring-mass system, unless the "spring" I use is of really thin material.

While at my local Lowe's pricing plywood to use for this project, they decided to give me a deal on "Soundstop" board, charging $3 per a 4'x8' sheet instead of ~$9, since the edges were chipping. I bought all 4 left on the spot.

Since using drywall will also decrease portability, I'm considering using plywood in combination with the soundstop.

Also, I'm considering using cheap bed mattress egg crate foam on the inside instead of the foam they're selling, although I'm not sure if it will help block out noise or reduce "boxyness" (though I'm hoping it will).


So, I'm planning to use plywood on the outside, (then a thin spring layer of ..?), then sound stop, then foam on the inside. I'll probably go with a normal box design rather than the one at the site, but modify the roof to use double layers for an "S" like ventilation system.

Or I could just follow the plans at the site, but using the materials I mentioned instead of what they say. (except this will cost more than the first due to needing more panels.)


So, now for my questions:

1. Would it be more advantageous to use the design at the site I linked or to use just one box with the top modified for ventilation? Will the ventilation on either allow much sound to leak?

2. How much sound would my design suppress? Soundstop supposedly has an STC of 23. Plywood supposedly has an STC of 26/27. With plywood/soundstop/foam, will it suppress enough sound to not be heard outside my room?

3. With Plywood's STC rating of 26 and soundstop's 23, would the two together result in a STC or 49 or just about 28? Would the foam even add anything?

4. Is there anything I could put between the Soundstop and plywood to increase the amount of sound blocked but without significantly increasing depth? Say without making it more than a 1/2 inch thicker? Money is also a factor here. Stuff like Mass loading vinyl would be expensive even if I was sure if it would help or not.

5. Are there any alternate plans for vocal booths I could use to accomplish my goal? Note, my closet is full and short, so that's not an option. Also, any alternate materials I could use?

Thanks.


Edit: Due to not wanting to increase the depth, I can't use studs or insulation. It seems the best combination without increasing depth would be drywall-green glue-drywall, but that would increase the weight too much, and I now already have soundboard. I certainly wouldn't mind buying a few tubes of green glue if they were to help performance, but from my reading it seems like it wouldn't help much with soundboard.

In short, I'm looking for the best possible combination for blocking sound while spending about $150 + the price of plywood.
 
Last edited:
your going to need studs to support the mass... 2x4 w/ r13 and line the studs and joists w. felt strip and use a layer of 5/8" drywall on each side. make 4 panels - one w. door. pin hinge them together and large rubber seals on edges. lay on a top panel (like walls) for ceiling. 4'w x 5'd x 7'h.

i'll post a new design doc later tonight or tomorrow
 
ok... better late than never :-)

this design uses several panels constructed of 5/8" drywall on 2x4 frames. they somewhat interlock with the base and top plates and use several carriage bolts per side to hold the walls together. the panels are isolated from the floor and ceiling with 1/8" neoprene. the panels are sealed to each other using the same neoprene or additional rubber seals (or caulk).

the idea being each panel can be moved into the space and stacked on the base, screwed together. top plate added, absorbers hung, plenums attached, and lights added. cables can come in through the top plate and are sealed with caulk.

the base plate is plywood on top of multiple layers of MDF on top of 4" 3pcf rigid insulation. the top plate is similar except for the insulation. the treatments are 2" 3pcf rigid insulation porous absorbers on each wall and ceiling. carpet on the floor.
ventilation is provided by 2 plenums at least one has a low SONE fan pushing air into the booth and the upper exhaust plenum could use another fan unit to pull. a well sealed exterior grade door with glass provides entry and view. probably about 40-45db real isolation - certainly enough for vox, probably ok for guitar and bass amps.

fan - something like http://www2.panasonic.com/consumer-...ns/model.FV-05VK1.S_11002_7000000000000005702
would work.










 
Couple of ideas.

1. Green Glue betwen the the layers of plywood, or drywall, will increase your STC rating without adding depth.
2. For portability, consider using a type of continuous hinge, aka piano hinge, on 3 of the corners. If your booth was 6' tall, get a 6' continuous hinge and use a type of acoustic door strip sealer along the edge so when the booth is set up, it is sealed. Leave one corner unhinged. That is the corner you will use to open the booth.
3. Build a separate foundation. Set the foundation on anti-vibration mounts (usually some kind of rubber, cork or foam). Set the booth on the foundation. The part where the booth meets the foundation should be a gasket seal, similar to the seal/gasket mentioned for the hinged corners. The weight of the booth will cause the seal to take place.
4. Build a hinged ceiling that also swings down to meet an acoustic gasket seal.

I have specs, but they exist in my mind, not on paper or on a file.

Let me know if you have any questions about any of that...

Thanks,
pianobenjjamin
 
More...

Also, for NRC inside the booth, consider ultra-touch denim insulation that you can adhere to the walls. The 3.5 inch R-13 has phenominal NRC ratings across the frequency spectrum. It is great for lows AND hi's. It has a 1.15 NRC. It also helps a lot with the STC, which will help with the sound heard outside of the booth and the room as you mentioned.

The con with this would be that it is 3.5 inches thick. You could restrain it with insulation bars...that would give it a slimmer profile. This insulation is made out of denim and is safe for use.

They also make a thinner insulation, but I haven't been able to locate any specs on the NRC or STC of the thinner material.

Acoustic blanket/sheets are pretty good too and have a very slim profile, adding little depth. But they NRC ratings are not nearly as good as something you would get from the ultra-touch. But I guess that all depends on how live or dead you want the sound to be in the booth.

Good luck!
 
Back
Top