John Sayers' Recording Studio Design Forum Archive

I'm building a one room studio inside my detached garage. I wanted to start a build thread but i didn't get any replies to the original post
http://www.johnlsayers.com/phpBB2/viewt ... =1&t=20963

The only info I think i was missing from that post was my SPL measurements and I just did them. But i have some questions still.

here is how I went about it;
using the Dayton iPhone microphone http://www.daytonaudio.com/index.php/im ... phone.html
and the AudioTools app > SPL Pro Digital Meter on C weighting - High Range and loaded the calibration file that goes with the Dayton mic.

the ambient noise inside the garage is 54dB mid-day on a friday

I set up my guitar amp (Silvertone 1482 with a 12" speaker) with a looper pedal in the middle of the garage, on the floor (where I think it might be when the room is built) and brought it up so that the loop was playing a guitar chord riff at 104dB when holding the mic at the walls of the garage about 10 feet away.

I went outside and measured each of the 4 sides of the garage standing about 10 feet back from each wall
right in front of the sectional garage door on the south side of the garage was unsurprisingly quite loud at 76dB
the east side where I have the hollow core pedestrian door was the loudest at 78dB (there is a 10ft corridor between this wall and my house)
the north side which backs up to a neighbor about 35 feet away was 73dB
the west side which also has a neighbor about 35 feet away was also 73dB

the outside ambient noise is 68dB mid-day on a friday so am I right in saying that when standing 10 feet away from my garage right now, my loud guitar amp is twice as loud as the ambient noise of my neighborhood?

I guess that I'm most surprised about the fact that the shell of the garage which is basically one sheet of 3/8" OSB T1-11 and 10 feet of space provides around 30dB of sound reduction. Not to mention that the construction was done to very loose tolerances (i can see daylight at many joints). So is the single sheet of OSB and the 10 feet that I'm standing away from the building really dropping the sound level that much? i mean it's not an error reading. It still sounds way too loud but it definitely is not like it is standing inside the garage. Did I do these measurements correctly? would you have done anything differently?

I think that i need to get 40dB of sound reduction in order to get it below the daytime ambient noise level. the night time ambient noise will be much less since it's really quiet here at night so rather than trying to get 60dB of reduction which would be impossible on my budget i will have to change my work habits in the evenings and just be quieter.

so, my plan is to build a room inside a room like this image that Stuart provided for me


with two layers of 5/8" drywall and r-13 pink insulation on the inside walls and one layer of 5/8" drywall on the two outside walls with more r-13 pink insulation on all of the outer walls. I don't know if i'll be able to do green glue with my budget yet but i'm trying to increase the budget.

My last question for this post is. Do you think i'll be able to get 40dB of reduction with this plan even though the outer shell is only one layer of 3/8" OSB?

I plan on caulking this leaky civ now and retaking the measurements just to see how much of a difference caulking alone will make.

For some unknown reason, I completely missed your thread!

Hopefully it's not too late to still be of help...

I guess that I'm most surprised about the fact that the shell of the garage which is basically one sheet of 3/8" OSB T1-11 and 10 feet of space provides around 30dB of sound reduction.

That's pretty normal, yes. You can't expect more than that from normal garage construction.

So is the single sheet of OSB and the 10 feet that I'm standing away from the building really dropping the sound level that much?

Actaully, you should measure about 3 feet away, not 10 feet away. So it will be a bit louder there, probably by about 5 dB or so... implying that your wall is only giving you about 25 dB of isolation.

Did I do these measurements correctly? would you have done anything differently?

Yes it seems you did them correctly, and the only thing I'd do different is stand about 3 feet from the wall when measuring outside.

so, my plan is to build a room inside a room like this image that Stuart provided for me

My last question for this post is. Do you think i'll be able to get 40dB of reduction with this plan even though the outer shell is only one layer of 3/8" OSB?

If you seal up both leaves air-tight, carefully, then you should be able to get better than 40 dB.

- Stuart -

Thank you Stuart,

No it's not too late because I sold my other house whilst I was still in the "sealing the shell with Alex Plus" phase and I had to move the contents of my old garage into the new one. Consequently my new garage is full of junk and I put the construction on hold temporarily. I need to start back up soon though, so your timing is perfect.

I'm encouraged by your comments that I should be able to get more than 40dB of reduction if I seal both leaves very carefully. That would mean that I could monitor music at moderate levels even at night, when it becomes rather quiet around here.

I will retake my measurements standing 3 feet away from the outside walls because I really want to know how effective just caulking the original garage structure is. You know,..."for science."

Too bad there is a 2-car roll-up aluminum door. Still not sure how to address that without sealing it off completely, (which is a non-starter with the missus). I know it has already been discussed elsewhere on the forum and I have read most of that. My original thought was that since the roll-up door is not part of the two leaves of the studio, (in other words it is on a wall on the opposite side of the garage than the studio) that it will not factor as much into the overall sound reduction. But I at least plan of putting some lightweight hard foam boards inside each of the panels to try and dampen it, as well as beef up the weather stripping. It will be opened and closed minimally. And a large set of full shelves will be sort of blocking 3/4 or more of the roll-up door to perhaps provide diffusion and absorption. Any new ideas about that would be appreciated? The next concern is for ventilation. There is a roof vent that I will have to seal off, i believe. At least the one over the studio ceiling (there is another roof vent in the other part of the garage which I may leave as-is or baffle). I plan on exchanging air with the non-studio part of the garage. I don;t have a good plan for that yet though. I was thinking of putting an exhaust vent in the middle of the wall adjacent to the garage space, at the ceiling, with flex duct and baffle box inside the wall cavity and an exhaust vent into the garage space somewhere? And then i need another duct w baffle box for a vent for air to come into the studio. I need to figure that part out. i need to figure it all out. I'm just blabbering at this point. I'm not asking you to design my studio for me. I'd rather come to you with a well thought out plan and ask you specifics about the feasibility and i realize that's not whats happening here. So thank you for everything again and i'll be back when i have a solid plan of action. thanks again,
Steve


below are images of the layout of the studio within the garage, showing placement of the doors of the studio and garage.

Too bad there is a 2-car roll-up aluminum door. Still not sure how to address that without sealing it off completely,

In your case, the door is fine, as it isn't part of your outer-leaf.... but you DO need to complete the outer leaf around your studio!

This is what you need, in order to have a properly isolated room: So you need to build the other two sides of your outer-leaf, then build the inner-leaf inside that...

The next concern is for ventilation. There is a roof vent that I will have to seal off, i believe.

Careful with that! It's probably there to ventilate the roof deck.... not a good idea to close that off. The roof needs ventilation, otherwise you'll start having all kinds of problems.

Your best bet would be to build a "middle-leaf" ceiling across the area where your studio will be... in other words, completing the outer-leaf ceiling above the outer-leaf walls shown above, to create the complete outer-leaf "shell". Then building your complete inner-leaf inside that: four walls and a ceiling.

below are images of the layout of the studio within the garage, showing placement of the doors of the studio and garage.

I would suggest moving the door forward a bit, to give you better space at the rear of the room for bass trapping and other treatment. It doesn't need to move much. Maybe a foot.

Also, you need to work on the arrangement of the furniture inside the room: Symmetry is key! The room needs to be symmetrical: left half = mirror image of right half.

Apart from that, it's looking good.

- Stuart -