Creating a Floating Sound-Proof (Sound-Isolation) Room

Question

I am going to build a sound-booth, 100% for recording spoken-word vocals. My biggest concern is sound isolation from exterior noise. I live near many major source of public transportation and they all make considerable noise. I am dealing with the following:

• I am 5 miles away (as the crow flies) from the world's 4th busiest airport, and am directly under a runway flight-path. That means planes are directly over-head all day long. The planes are usually of the 737 variety with a big 777 or 747 a few times per day. (I can take a break when a mega plane goes by, but I don't want to hear the 737s.)
• I am one city-block away from two major commuter train lines serving a mega American city. They make some noise, but not as much as the planes.
• I am half a city-block away from a major interstate. I only really hear it at night because day-time traffic keeps trucks from going too fast and making too much noise.
• There is some street noise, but it's not a very busy street so it's not bad.
• My studio is in an attic that has no (thermal) insulation whatsoever. There is an asphalt-shingle roof on top of plywood. Inside there are wood-stud walls covered with a single layer of thin drywall properly finished and painted. There are a couple of old, drafty, wood windows with single-pane glass. The sound isolation from the building is quite poor. I am not allowed to make improvements on the building.
• I prefer to record with a condenser mic because I want very little noise in my recordings. My mic-of-choice has an equivalent noise level of 4dB-A, so it can pick up soft noises.
• I am not dealing with any noise from people, instruments, etc -- just the planes, trains, and trucks.

I really only need a small sound-isolated box in which I can sit and record. I've determined a 4 ft x 4 ft x 5.5 ft (exterior dimensions) box will be adequate for my needs. I am trying to determine the best way to configure 4 layers of drywall, a 5-gallon bucket of Green Glue, some OSB, and some 2x4s to best deal with the rumbling of the planes, trains, and trucks.

So far I have come up with two designs:

In my designs, the black blocks on which the rooms stand are neoprene setting blocks (used in commercial glazing to hold massive panes of glass for decades). The dark-brown horizontal boards are 3/4" OSB. The light-brown vertical boards are 2x4s framed sideways (so the depth is 1.5 inches rather than 3.5 inches to maximize interior space). The dark gray panels are 5/8 inch drywall. The green lines are Green Glue.

Design A is a room-in-a-room 4 layers of drywall sandwiching 3 layers of Green Glue. Design B is a room-in-a-room-in-another-room. The only part of either design that touches any of the building are the black neoprene setting blocks -- no part of my designs touches a wall or ceiling. With the drywall on the floor and the stair-step joinery, I have tried to eliminate any potential flanking noise.

Most advertising literature about Green Glue recommends something like Design B. However, I have also read that when dealing with low-frequency noise (like planes, trains, and trucks), a single wall of mass like design A could be better for isolating noise.

So my questions are:

1. Which of these two designs is better for isolating the plane, train, and truck noise?

2. Do you have any tips/advice/comments about either design, and how I could make either one better?

3. Is there anything here you'd consider "overkill" or otherwise too extreme for my conditions? (Maybe 3 layers of Green Glue is unnecessary?)

Thanks!

Answer 1

i don't think you are in a bad situation at all.

first of all a very usefull forum by mr John Sayers. http://johnlsayers.com/phpBB2/index.php <- read a lot here!

Blocking the sound needs mass as stated but there are solutions that don't require 1meter o cement just to block some noise.

What you'll need is neoprene blocks , gypsum boards , and insulation material(rockwool/fiberglass).

To set up correctly , rather than describing the sounds , use a microphone and get the profile of the sound that bothers you. How loud is it in the room ? (db) , and what are the frequencies that's passing through the walls.

This will help determing the STC you are going to need.

http://www.tmsoundproofing.com/soundproofing-basics.html

The brute force of stopping sound is insane mass, or air loss. But the more developed ways inlcude materials that actually vibrate when sound passes through them thus spending the sound waves energy , also after the vibration there's dampening material needed.

What you want to build is a series of variable rigidity obstacles to stop and disorient the sound at every step to the final silence.

You are going to need 100% shut setup meaning no air coming through, this is not too hard to be accomplished when talking about walls , but it is hard to be accomplished when talking about doors, you'll need a good shut door , possibly with a rotational handle that presses more as it's turned, many times used in industrial fridge doors.

One of the better designs you'll eventually come across is the "Double leaf" design

which as you can see , has 2 adjacent layers with insulation , air gap , and 2 more layers.

Here is a very detailed STC Chart by mr Sayers.

http://johnlsayers.com/Recmanual/Pages/STC%20Chart.htm

Also the construction manual by Mr Sayers again.

http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm

There's a lot to read and understand , but your task is totally do-able if you ask me!

Good luck

Answer 2

Sound is blocked only by mass. Either solid mass, or air mass (over a distance). Of the two alternatives you have shown, certainly you have more chance of success with the solid option vs the hollow option. If you were dealing with nearby (physically conducted) higher-frequency sound, then the air-gap might be of some benefit. But you are dealing with large-scale environmental low- and mid-frequency, broadband noise. So the more mass you can achieve, the better. Don't forget to completely cover the windows. Attempting to preserve them while blocking out sound seems rather beyond your budget and constraints.

Frankly, up in the attic (closest to the aircraft noise) and in a rented space where you can't do much physical "remodeling", I can't really hold out much hope that you will achieve a noise floor adequate for your desired results. Certainly put in as much mass as you can achieve to block ambient noise. But you may have to use a headset microphone to boost your "signal-to-noise ratio" by an order of magnitude over traditional 19th century techniques.

I highly recommend viewing this program with guest George Whittam, home recording studio engineer to the stars. They discuss many aspects of setting up a home recording studio.

They mention that many voice artists doing long-form recording (books, etc.) find that recording in the middle of the night to be much quieter than during the day. But you have rather knocked that option out of the box. You really seem to be in a very bad location for what you are trying to do. And with show-stopping restrictions on the options available to alleviate the problems. Good luck.

Answer 3

Honestly, I would look for an alternative place. Could you not rent an office space or somewhere away from all that noise?. Sound isolation is expensive to pull off, there is no cheap way to do this. I had to shut my studio because it was based on an industrial estate that became intolerably noisy. It's worth a go I suppose but I don't think you'll have much luck.

Answer 4

Instead of building your own, look for a used audiology testing booth, commonly used for assessing hearing. The advantages are many: It will attenuate sound below audibility across the entire frequency range at guaranteed levels, minimize the pronounced resonances inside your box, provide silent forced air ventilation, and give you a window and light. I used this approach rather than build an announce booth for a television studio at a medical school. It was dead quiet inside, so much so that we had to add reverb to naturalize the recorded sound!