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I'm glad I don't live with another home workshopper. Just think of what it would be like to endure the sound of whining machinery endlessly blaring out from the workshop on evenings and weekends -- without the fun of building anything yourself. Why our families put up with us is a mystery to me. I wonder if anyone has ever collected data on the divorce rate of woodworkers relative to the proliferation of power tools. The two are probably skyrocketing together.
While noise is an inevitable part of modern woodworking, there are things you can do to reduce the burden it inflicts on your housemates. Although you won't be able to build a completely soundproof basement shop, significant sound reduction is still an attainable goal. Yes, it'll take some work, but if the comfort of your family isn't incentive enough, then think of the exercise as a bargaining chip. If you let me buy that new 18 volt, variable-speed, reversible cordless drilldriver with 15 minute quicker charger and metal case, it'll let me put up some drywall that'll make the shop much quieter. Pleeeease.
Understanding the Noise Problem
Engineers measure sound intensity in decibels (dB) and that's the yardstick we use to rate the noise generated by all the tools we analyze in our performance reviews here at Canadian Home Workshop magazine. The lower the number, the quieter the tool. Most machines we review put out 85 to 95 db during use -- about the same as a noisy factory or an unmuffled truck. Thickness planers are growing in popular these days, but they're noisy, too, regularly topping the 100 db mark during mid-cut. Although 130 dB is considered the threshold of pain, my ears always hurt unless I wear hearing protection in the shop. I prefer ear muffs during short jobs -- so I can easily take them off and listen to the radio again. For longer stints at any machine I use the roll-and-insert foam ear plugs because they don't interfere with the arms of my safety glasses. To really pamper your ears, try both ear plugs and muffs. It's like being in an isolation chamber.
There are two things to consider in your noise reduction campaign: the elimination of all cracks -- even tiny ones -- leading out of your workshop, and beefing up the sound resistance of walls and ceilings. It's hard to beat the performance of drywall as a surface covering on both these counts. Its ability to absorb sound is considerable, thanks to its density. Drywall tape and joint compound also seal sound-transmitting, board-to-board cracks. My favorite type of drywall for workshop applications is 5/8-thick fire-code material, the kind required for commercial applications. Besides being thicker than usual, the gypsum core includes glass fibers for extra strength. Fire-code drywall costs about 20% more than regular 1/2 stuff, but it fares much better in the rough-and-tumble workshop environment.
Although there are several ways to measure sound resistance, the most appropriate yardstick for workshop situations is a scale called the Sound Transmission Class (STC). This rates the minimum sound resistance of a floor or ceiling at all frequencies. The greater the STC, the more effective the blocking of sound.
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A 2x4 wall covered in 1/2 drywall, for instance, has an STC of about 30 -- not even enough to prevent loud speech from being understood from a neighboring room, and certainly not enough to preserve domestic bliss in a home workshop situation. The standard type of open basement ceiling, with exposed joists and subfloor, is even worse. You might as well be woodworking underneath a bongo drum.
Beefing Up the Ceiling
Since most of the sound that travels up from a basement shop comes through the floor, it makes sense to focus your resources there, at least initially. And as you'd guess, simply putting 1/2 drywall on the underside of the floor joists boosts STC of the whole floor structure to only about 36 -- not nearly enough. A better option is to install 5/8 drywall onto the floor joists, along with sheet metal strips call resilient channel, as shown here. These channels separate the drywall from the floor joists, blocking sound transmission more effectively than direct drywall-to-joist contact. Adding fiberglass batts between the joists before drywall installation will boost the entire floor to a pleasant STC of over 50.
Sound-Resistant Partition Walls
Unless you're lucky enough to have the whole basement for your hobby, partition walls will be part of your workshop design. You should aim for a wall design that delivers at least 40 STC. A 2x4 wall with a double layer of 1/2 drywall on each side will do that. Far better, however, is the double-stud wall shown here. It delivers a whopping 50 STC even without internal fiberglass batts that can boost sound resistance further. Loud speech is not even audible through such a wall. The design is based on a 2x6 top and bottom plate, with staggered 2x4 studs spaced 8 apart. That sounds awfully close together, I know, but don't forget that the studs are staggered. They actually provide nailing surfaces that are the standard 16 from centre-to-centre on each wall face. The idea of the staggered studs is to eliminate the continuity of wood from one side of the wall through to the other. Sound is transmitted best through the vibration of solid materials, so the more you can eliminate this travel route the better.
Another feature of my favorite quiet-wall design is the use of a sound-deadening layer underneath the drywall. The best material for this is the kind of fiberboard sheet materials sometimes used as exterior wall sheathing under brick veneer. Although this is usually coated in tar, to increase weather-resistance, it's also available uncoated for interior use. The combination of hard, dense drywall and soft flexible fiberboard underneath works well because it creates very different, side-by-side densities. Sound engineers have discovered that this kind of material diversity is a potent noise blocker. You'll need longer-than-normal drywall screws to secure such a combination to wall studs, but if you can't find any, don't worry. I know from experience that regular, flathead wood screws work fine for securing drywall, and they're easy to find in longer lengths.
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