About the House: Soundproofing Against the Garage Band Next Door

By Matt Cantor
Thursday January 28, 2010 - 08:56:00 AM

I think of myself as one who lives to revel in the sounds of the world, much of—if not all—the time. I don’t want to live in an anechoic chamber, devoid of sound, devoid of the joyful noises of NPR and of Dexter. Screaming is good. I like screaming. 

Well, then again, there’s my cat Mitochondria. He’s been keeping us up with his incessant attempts to speak English. He’s getting close, though I wish to heavens he’d take a break between midnight and 6, but apparently this groundbreaking work must be impeded by neither man nor beast, and my personal needs, as well as those of my poor wife, are insufficient to earn a place in the calculus. Soon I’ll have to be hospitalized, but that, too, is another story and well off our topic du jour. 

We have spent a good deal of time in the past discussing the issue of sound control in buildings. Google and ye shall find. But things have advanced to some degree, and since there’s a bit to add to this story, I thought I would revisit some of the basics and discuss a couple of new products that can help suck up decibels. And, perhaps, decrease inter-apartmentmental violence. 

Most sound in buildings is conducted between rooms or apartments by the materials that make up the building. These materials have very different properties in terms of sound transmission or absorption and in terms of the types of sound that they tend to transmit or absorb (high versus low frequencies to put a blunt point on it). We won’t go into that last part too much, but it’s important to keep in mind if you’re shopping for building materials in response to a particular problem.  

If you are working with a general contractor, an architect, an acoustical engineer or a material provider, it’s good to let them know the specific kinds of noise you’re trying to kill off in order that the right materials get used. All sound deadening is not created equal. 

Among methods that have been popular for decades are double-wall construction, party-wall construction, soundboard, plain old drywall, insulation and resilient channel. There are certainly other methods but these are the most common materials and methods that I’ve seen used in residential and even commercial construction in my time. Today, there are a few new items on the shelf, including specialized drywall or plywood that includes plastic and metal layers. We’ll get to those a bit later, but they’re the reason I’m on this tangent today. 

So, what the hell do I mean when I say, double-wall or party-wall construction? These are fairly simple to understand. For double-wall, it’s simply that instead of building a single wall between two rooms (or two apartments) you are building two. These can be built very close to one another but are usually spaced a fraction of an inch apart. This means the loss of roughly 4 inches of space on one side of a room. But if sound control is important, it may be well worth giving up.  

Double walls often have finishes on one side of each wall and no finishes between the two. But a dogged designer may opt for drywall between the walls, as gypsum is a good sound-absorber and helps us to achieve a higher sound transmission class (STC) if that’s our aim.  

Some communities, code agencies or overseeing bodies will demand a given STC between the apartments in a complex or on the walls of an industrial facility in a mixed neighborhood. It’s good to have standards, though some have criticized this nearly 50-year-old standard for being over simplistic and lacking sufficient attention to very low frequencies like sonic booms and all of James Cameron’s movies. 

I will also mention a personal favorite (because I did it several times, and this means that it had to be the smart way, right?) and that’s the party wall. This has nothing to do with drugs, rock and roll or that other stuff that I can’t remember anymore. It’s a wall that’s wider than the typical one, with studs that don’t line up. Half the studs push toward one side and half push toward the other side. The studs on this wall literally zigzag back and forth every few inches, so that the drywall on one side is supported by every other one and the drywall on the other side is supported by the others. The result is that the wooden studs supporting one side don’t touch the other side. This cuts way down on sound transmission since most of the wall doesn’t touch both sides. This is very much like a double wall but only has to be a little wider than a single wall. 

In the case of both of these wall systems, filling the wall with insulation can make a big difference and is often used to increase that STC rating. No matter what you’re doing to deaden sound, adding insulation in the wall or floor assembly is always a good idea. 

Resilient channel, and now a range of competing clips, is designed to hold the drywall away from the stud or joist (the wall framing) in order to insulate these parts and further inhibit the transmission of sound waves or sound energy. This is a very cheap method, as resilient channel is nothing more than a long (they come in 10-foot lengths the last time I checked) folded bar of thin metal that provides for two connections. One is to the wooden framing (or metal framing if that’s your orientation), and the other is to the drywall or other finish (though drywall is queen in this world). An entire room can be drywalled this way in an extra hour or two adding on very limited cost with fairly good results. If asked to spec a sound reduction, I would be hard-pressed not to add this simple item to my array of tactics. 

Drywall itself is a very effective sound-deadening material, though concrete is the gold standard, and if you’re really serious about sound isolation you’re pouring concrete. Additional layers of drywall can rapidly increase your STC (it’s an increasing scale—a high number means low sound) so this is a very common choice when designing for low sound transmission. Also, drywall, aka sheetrock or gypsum board, is very inexpensive, and, since it comes in 4-by-8-foot sheets, a room can be given additional layers prior to taping, with very little time and expense. 

Soundboard and its various cousins, all soft wood-fiber panels, deserve a very short mention. They absorb sound waves in the same way that fabric does, and they tend to work better with high frequencies than with low. Soundboard is cheap and can be applied behind drywall to add one more phalanx in the battle against the garage band next door (or in keeping those Philistines who can’t appreciate your genius from calling the cops while you create). 

This last method was, apparently not good enough for some group of engineers, so the meddling began, and what came out of the lab was QuietRock. QuietRock, a product of Serious Material in Sunnyvale, sells for $40 a sheet and up. This will vary with the specific product and volume, so I would expect your price to be significantly higher on a residential remodel. Now, this is much more expensive than drywall, but has some extremely cool features. Quiet-Rock varies in style but is generally made up of two thin layers of drywall that have been bonded on either side of a specialized “visco-elastic” polymer that isolates the two sides so that sound waves get lost in between. Some versions add a layer of steel, making cutting and installation somewhat more complex, but it can also add RF or EMF control, which is very exciting. If you really want to shut out voices that are telling you to do bad things or prevent alien control, this is the right material. But seriously, these are very exciting new technologies and may be well worth the cost, given that they can control weight and add shear strength. They can also isolate EMF that can cause problems with electronic systems and cut out the sound of equipment, plumbing and whatever irks you. 

Serious Material makes doors, windows, adhesives and a full line of materials, and the company is worth taking a look at if sound is what you hate. As for me, I’m going to try to get some sleep after Mitochondria and I work on his English just a little more. 


Matt Cantor owns Cantor Inspections and lives in Berkeley. His column runs weekly. 

Copyright 2009 Matt Cantor