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December 2014
more... How-TosRecording TipsGuitar TracksMay 2013

Keeping the Peace, Pt. 2

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Keeping the Peace, Pt. 2

This is probably not a good place to shop for acoustic treatment and soundproofing materials.
Photo by Francine Girvan, Wikipedia Commons

In last month’s column, Keeping the Peace, we began exploring the issue of sound control. We looked at both controlling the sound from amps and other instruments that bleeds out from our space and controlling external noise from wafting into our microphones when we’re recording. You may have just noticed that I didn’t use the word “soundproof,” which implies that sound is completely stopped cold in its tracks and prevented from leaving or entering the room. In the real world, achieving a truly soundproof space is extremely difficult and extremely expensive. But what we can do is knock down the level of sound that is escaping from or coming into the room.

A professional acoustician will have a large bag of tricks to draw from to achieve sound control. There’s a lot of science, education, and experience behind what those guys do. If you can afford to hire one to create a studio for you, I highly recommend it! But whether you hire a pro or do it yourself, there are several components to controlling sound that we can address. What will work for you all depends on your specific space and situation.

Mass — Sound travels by vibrating materials. Whether we’re talking about air, water, metal, drywall, wood, or whatever else, the principle is the same. It probably seems obvious, but the more mass a material has, the harder it is to make it vibrate. It’s also a matter of how inert a material is and where its resonant frequency falls. For example, a thin brass pipe might ring like a bell when struck, because it vibrates easily. On the other hand, a sheet of lead probably won’t ring at all, no matter how hard you strike it. One of the main components of sound control is mass. But it has to be mass that is installed correctly to prevent resonance. In studio design, for example, you might use two layers of drywall on each side of a wall to increase the mass of the wall, instead of just a single sheet.

Air Space — Air between two boundaries (such as between the sheets of drywall on the two sides of a standard wall) helps to control sound transmission. The bigger the air space, the better. The key here is making sure the boundaries on the two sides of the air space aren’t resonating.

Decoupling — This has nothing to do with breaking up with your significant other over noise issues. Decoupling means preventing the vibrations in one surface from causing another surface to vibrate. Many of us use foam pads or other decouplers under our studio monitors to prevent vibrations from being transmitted into the desk or stands on which they are sitting. In pro studios, the floor and even the walls and ceiling might be mounted to springs or rubber pucks to prevent vibrations from propagating.

Tight Seals — Sound can travel through the smallest of openings. The more airtight you can make the space, the more you will control the sound. Be it gaps around and under doors, AC outlets punched through wall surfaces, or holes cut for lighting fixtures and light switches—all of these and more can reduce how tightly a room is sealed. Let’s also not forget about heating and cooling vents and returns. Sound will travel right through these into the duct-work, and from there, throughout the rest of the building.

Mythbusters

When it comes to acoustics and sound control, there are a lot of myths floating around out there. So let’s bust a few of them.

Acoustic foam or fiberglass panels will help with sound control.
FALSE. Absorptive materials, such as acoustic foam, will do the job of taming and tuning the acoustic response inside your room, but will do little to prevent sound from escaping into the outside world.

Egg cartons can be used for sound control.
VERY FALSE. Let’s not even go there. Egg cartons are for transporting and storing eggs.

Using carpet on the walls and ceiling is a good option for sound control.
FALSE. In fact, from an acoustic standpoint, carpet on the walls and ceiling is generally a bad idea inside the room because it’s a poor acoustic absorber and will do next to nothing in terms of blocking sound from escaping.

Now that we’ve looked at some of the components of sound control, we can begin to look at how to utilize or address those components in our spaces to cut down on noise escaping or entering. Tune in next month, we’ll get started!


Mitch Gallagher's latest book is Guitar Tone: Pursuing the Ultimate Guitar Sound. He is the former Editor in Chief of EQ magazine. In addition to being a writer, he is a freelance recording engineer/producer/ mastering engineer, teaches music business and audio recording at Indiana University/Purdue University, and is Sweetwater’s Editorial Director. www.mitchgallagher.com
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