One of the single most annoying inconveniences that most musicians who practice at home must face sooner or later, bar-none, is that finicky neighbor. That one guy or gal on the block that would rather listen to paint dry than some primo, home-made jams. The one that will speed dial the local police before more cowbell has even been suggested! Although soundproofing isn’t exclusive to the world of noisy musicians, they are the usual suspects when it comes to religiously needing rehearsal space that won’t draw spite from sound sensitive neighbors – or roommates, for that matter. Furthermore, soundproofing isn’t just a great way to keep sound in but also just as effective in keeping sound out as well; definitely a huge plus if you are planning on recording without any outside noise pollution from cars, kids or what have you. Yes, when a proper studio just isn’t in the cards, soundproofing a home rehearsal/recording room is by far the next best thing.
When planning your soundproofing project it is helpful to remember some basic science about sound. Sound can be defined as energy created by some sort of mechanical vibration. The three factors that are involved in reducing sound intensity are air, mass and distance. Distance is something you probably do not have too much control over while preparing to soundproof your room. Most home-made projects to soundproof a room are going to be focus specifically on air and mass. Mass is very important in soundproofing because heavier objects stop more sound than lighter objects (although one exception being fiberglass insulation). The general rule of thumb is that if you double the mass of a wall only half the sound will be transmitted through to the other side. However, remember too that as the frequency of the sound lowers it becomes more difficult to isolate. For every one octave drop in pitch the sound reduction is reduced by half. This is why you can hear the bass sounds coming out of a concert a lot farther than any other frequency.
Most walls and ceilings conduct sound rather easily. A typical wall or ceiling is constructed a lot like a drum or guitar - center studs (much like ribs) surrounded by plywood or sheetrock (much like membranes). The empty cavity between the membranes conducts sound very well – too well, in fact. This makes soundproofing a challenge. There are of course construction techniques that can be implemented if you are lucky enough to be in the position of building a new room. One approach that is recommended frequently is to build a 6-inch interior wall with staggered studs rather than a traditional 4-inch interior wall. A traditional interior wall is constructed using 2x4 studs with plaster or sheetrock on either side. This construction method allows sound to travel through the wallboard and directly through the studs. The staggered wall uses a 2x6 across the top and bottom of the wall with 2x4 studs from the floor to the ceiling. The 2x4 studs are staggered so that every other stud is against the wall on either side; therefore, no stud carries the sound all the way through to the other wall. This is feasibly the most effective way of isolating sound from traveling from room to room. If you are undertaking a complete renovation this may be something to consider, but chances are most of you out there aren’t ready to drop that much scratch in order to simply quell down complaints from fussy neighbors.
Most true sound studios are built as a "room within a room." By building a smaller room within a larger room it is possible to isolate nearly all noise transmission. However, most of us simply looking for a place to jam or record are probably not interested in this type of extensive modification. An easy place to start when soundproofing your room is to seal all holes and cracks in your walls. This is an important step that is too often overlooked. Check around windows and doors, pipes and wires, heat vents, light switches and electrical boxes. Cracks or gaps in any of these places can allow a lot of sound to pass through. Fill any gaps of cracks with an appropriate filler like insulation, foam or silicone caulk.
Upgrading your doors can also make a major difference in soundproofing. Most interior doors are hollow-core. Hollow-core doors do virtually nothing to limit sound transmission. Solid-core doors (whether solid wood or filled with another material) allow far less sound to travel through. Even with a quality, solid-core door you may need to weatherstrip around the door though. Sound will readily travel through the gaps under and around the door. Careful weatherstripping will provide a tight seal to help soundproof your room.
Windows present a special challenge to soundproofing. Double-pane windows represent a significant improvement over older, single-pane windows but still allow a lot of sound to pass through though. Heavy drapes may help somewhat but will not fully block sound either. The only real option for windows is to use heavy glass or to completely close in the windows. This may not be an option but at least upgrading to good double-pane windows will help with soundproofing. Make sure that you have a good seal around the windows as any gaps around the windows will allow noise to pass through.
Insulating all interior walls with fiberglass insulation with help to soundproof the room. Filling the wall cavity with fiberglass insulation greatly reduces the sound transmission through the wall. Unfortunately this usually means removing the existing sheetrock or plaster to install the insulation. However, the benefits of adding insulation will definitely help your soundproofing project. Using a double layer of sheetrock (gypsum wallboard) will also help limit noise transmission. Alternating directions of the sheetrock will also improve performance. Apply one layer of sheetrock in a horizontal direction and the other layer in a vertical direction. Non-hardening silicone caulk can be applied to all studs before mounting the sheetrock on the wall as well as between layers of sheetrock. The non-hardening caulk reduces sound transmission further.
Consider insulating the ceiling space above your room as part of your soundproofing project. You may also want to explore using acoustic ceiling tiles in your soundproofing project. Acoustic ceiling tiles are available in a variety of styles. You are not limited to institutional-style suspended ceilings. These tiles can help reduce noise traveling through the ceiling and make your room more soundproof.
There are two rating systems commonly used to describe the noise-limiting qualities of construction materials. Sound Transmission Class (STC) rates materials with a number based on how well the material blocks sound. A higher the number represents less noise transmission. For example, a hollow-core door or single-pane window may have an STC of 20 while a painted, eight-inch, concrete block wall will have an STC of 46. The Sound Reduction Index (SRI) uses decibel measurements. The higher the decibel rating the less noise will pass through the material. For instance, a light-paneled, interior door may have an SRI of 15dB while a brick cavity wall that is plastered inside may have an SRI of 50dB. These rating systems are very helpful in comparing windows, doors and other materials.
Of course, if you aren’t exactly the type who handy man or woman who knows the difference between a brad nail and finishing nail or are living in a place where any sort of physical modification is prohibited, there are always easy to use soundproofing kits available that require nothing more than your hard earned cash and the ability to place stuff on a wall. These kits usually come with different types of 4x8 sheets of foam that should provide a decent amount of soundproofing without having to remodel an entire room. It’s not the most effective solution, but better than nothing!