"RicodJour" wrote in message
oups.com...

Your design is going to be more of a problem than I think you realize.
There are all sorts of problems with it:
- door swing clearance on a 4.5" thick door. What sort of gap is
required and how does that affect the sound transmission?

I wondered about that. Looking at a door that's about 1 3/8" thick, watching
the gap between the door and frame, focusing on the corner which butts up
against the frame (which is the part that matters) the approximately 2/16"
gap actually seems to be overkill. If I take a wooden mixing stick that's
just a gnat's hair narrower than the gap and open the door, there's no
contact with the stick. Cearly the geometry is such that this edge never
gets any closer to the door frame while it's being opened.

I think I just have to make sure the placement of the hinges creates a
similar geometry on the sound booth door. Should be simple enough to work
out using an overhead view paper model of the structures involved. Shortened
of course, it doesn't actually have to be as wide as the door is. That inner
edge of the door is either going to get closer or it isn't, doesn't matter
how much of its length I look at. The drywall on the inside won't be an
issue since it will already be cut back a bit to accomodate the magnets.

Anyway, as far as sound transmission, I can use gasketing in the gap that
the door will have to brush against or and/or an exterior flap that fits
flush against the exterior when the door is shut, plus the flush-fit
interior door stop will act as a sound barrier.

- regardless of what 2x4s you use, they're not furniture woods, and
always have a bit of twist or warping in them. At almost 4' wide even
a little twist will leave a gap, and even a little gap lets through a
_lot_ of sound. My acoustics professor would tell us that acoustically
speaking an 1/8" gap at a door is essentially the same as leaving the
door open.

Hopefully "machining" the edges with the table saw to get them very
flat/square and making all the end cuts as exact/identical as possible with
the miter saw will reduce this significantly.

- the more I think about it, the less confident I am about my earlier
advice about the hinges with a door that size. It's the width of the
door that is the biggest factor, not the weight. I think I'd go with
two pair of hinges to be on the safe side.

10-4.

- drywall on a door is not a good idea. The surface is not hard enough
to stand up to the abuse a door takes. If you want to tiptoe through
the door every time you use it, it might be okay, but people push doors
open with their hips when their hands are full and the facing paper
will tear. I don't think it will be too long before the door looks old
before it's time.

The drywall shouldn't take any abuse. I should have mentioned that it's
likely only going to be me that will be using this sound booth. I'll have
handles installed inside/out. I don't run a commercial studio. Just a
hobbyist fooling around.

I'm not sure how critical your soundproofing requirements are, but a
standard arrangement is to have two doors with one hung on either side
of the wall. The separation is at least as important as the doors
themselves.

Well, my "second door" is the existing door of the room, which is itself
already inside a house. Ultimately, I just want to cut down on the low
frequency noise that comes in. It's actually not bad now, but I want to make
it better. Some sound booth schemes call for more elaborate measures, more
drywall, bigger gap, "floating" floor, but I believe they're going on the
assumption that you've got a studio that's in the middle of a city - so even
if an ambulance goes by outside or someone fires up a jackhammer, it won't
be heard within the studio. I'm in a quiet suburban area, and what low freq
noise I get is mostly from distant traffic.

Keep in mind, when I talk about "noise", for the most part it's nothing you
could hear with just your unaided ears, unless a plane goes by overhead or
something. If you sat in the room now in the dead of night, you'd consider
it absolutely silent. But when the mic preamp is cranked to record acoustic
guitar, there is low freq rumble that registers on the VU meters of the
recording software and can be heard on the monitors when A/B comparing it to
no input from the mics. I'd be happy if I could subtract another 10 - 15db
or so from the noise floor, which I think is possible (hopefully). Of
course, I'll be treating the interior of this booth as well to deal with
sound reflection within the booth itself.

There's one window in the room, for which I made a "plug" out of acoustic
paneling, lumber and foam. That alone cut down the noise so much (probably
by over half), it gave me the idea that this booth would for all intents and
purposes given my surroundings, give me a totally silent area so that the
only noise would be the electrical noise of the signal chain - mics, preamp
and system (no system is completely noise free). The computer I use is in a
separate room and is essentially a non-issue given the way it's situated.

Why don't you tell us what the application is and what the room will be
used for?

See above.

The door is an oddball size, as is your intended
construction.

I decided I wanted it big for a couple of reasons - It will give me elbow
room for moving mic booms, guitar, music stand etc. in/out without banging
things and I'll be able to mount the outer edge stop using the 2x4 that will
already be supporting the other sheets of drywall that will comprise the
rest of that wall.