Most musicians will admit to sharing a single core skill necessary for mastering their instrument: control. When it comes to designing spaces for practicing, performing, recording or just jamming, control is equally important to acousticians and architects. We aim to control the sound entering and exiting the studio, the heat and humidity inside and, of course, the acoustics.
While a home music room may not have the demands of a professional recording studio, many spaces can benefit from the sound isolation and acoustic treatment applied to rooms designed for playing music. I’ve designed spaces for music at all scales, from auditorium halls to private listening rooms, and have learned a few basic sound concepts that can dramatically improve the aural environment of any space.
Understanding the use of the space is the first priority. A practice space for your garage band and a space used for vocal recording or listening to chamber music will have some obvious differences.
The location of the studio space will greatly affect the degree to which you’ll need to isolate it from the rest of your home. Imagine how the sound isolation requirements for a practice room located next to the nursery versus one in the garage might differ. No amount of acoustical caulk is going to make the former practical. Sensibly locating the music room is step one.
More informal performance and practice spaces are usually more concerned with containing the sound transmitted from them to adjacent spaces, as well as with sound fidelity and instrument housing – and some instruments can be quite large. For these spaces, isolation construction strategies and controlling how the sound behaves in the space are more important.
The next part of planning is defining the actual proportions of the space. There’s much debate in the acoustical design community regarding the ideal proportions, and the math gets complicated quickly.
For the casual audiophile, it’s generally accepted that the Greek golden mean proportions of 1:1.6:2.6 (height by width by length) will yield an acoustically pleasant room. As an example, if we begin with a typical 8-foot ceiling height as a starting point, we should aim for a room that’s roughly 13 feet by 21 feet.
The space shown here makes use of a clever device that can alter the shape of the room and its acoustics. The pivoting panels seen at the rear wall of the stage area can be used to fine-tune the geometry and control the way sound is reflected around the room.
- Larger volumes are always better than smaller ones.
- Avoid completely regularized forms. Perfect cubes and long, narrow spaces with parallel walls are poor acoustical performers.
- Irregular shapes and surfaces (walls, floors, ceilings, bookcases) as well as convex forms allow sound to be diffused in a space, which is desirable.
- Avoid concave surfaces, which tend to focus sound.
- Avoid room dimensions that are direct multiples of one another (1:2:3) – for example, a 16-foot by 24-foot room with 8-foot ceilings – because they will amplify resonating frequencies, making for an acoustically muddy and noisy space.
- Avoid parallel walls and flat ceilings. These are generally considered a bad thing in acoustical design because parallel walls turn a space into a tennis match of sorts, bouncing sound waves back and forth between the wall surfaces and causing echo and flutter. This is one reason performance halls are shaped the way they are with splayed walls, floors and ceilings.If you’re repurposing an existing space with less-than-ideal room proportions, don’t worry, absorption strategies can help to overcome this shortcoming (more on this later).
When sound waves strike a surface, three things happen:
1. Some of the sound is reflected back into the room.
2. Some of it is absorbed by the material.
3. Some of it is transmitted through the material. These are the three main things we control when designing a space for music.
Hard surfaces reflect and disperse the sound energy in a space; soft surfaces absorb it. Much of contemporary architecture is defined by hard lines and surfaces, like concrete, hardwood and drywall.
These are all highly reflective surfaces. The bouncing of sound is known as reverberation. For a live recording environment, a certain amount of it can be desirable. But reflection generally needs to be controlled. This is especially true for smaller music rooms so it doesn’t render the sonic nuances of the music unperceivable.
To reduce the sound energy in a space, we use absorption. Rugs, drapery, couches and wall hangings all help to absorb sound, especially at higher frequencies, which are usually perceived as unpleasant.
Absorption in a room controls reverberation and reduces ambient noise. In spaces without a lot of furniture or drapes and many hard surfaces, special acoustic absorbers (foam, acoustical plaster) can be used to deaden a room.
Absorption shouldn’t be confused with our next control point: isolation. Adding absorbers in your garage won’t keep the sound from being transmitted to your neighbors; it will only improve the way the space inside sounds.
To keep the peace with your neighbors, you’ll need to focus on isolation. Because sound is transmitted by vibration, it makes sense that to minimize sound transfer between spaces, we should minimize their points of contact. In standard wall construction, walls that separate spaces typically share framing members — the studs. To truly isolate a space acoustically, you want to keep the perimeter framing of each space independent from the adjacent spaces as well as from the surrounding structure. This includes the floor and ceiling.
Many acoustical designers refer to sound isolation in construction as decoupling. The goal of it is to keep the sound waves from touching the structure of a home and allowing it to vibrate.
- Use floating walls that are framed independently and isolated from the surrounding structure with special padded isolation clips and hangers
- Isolate the mounting of materials using resilient channels and wall clips to hang drywall
- Isolate the vibrations induced by building systems like plumbing pipes, electrical appliances and mechanical equipment
- Add an air space between walls to create a sound-isolating medium
- Seal all the joints, including electrical outlets, studs, drywall doors, windows and trim
- Use specialty acoustical products like membranes, mass-loaded vinyl, underlayments and acoustical insulation
- Use special insulated duct treatments and grilles to minimize air noise
Think of your room as being like a fish tank: Any openings, even small ones, that aren’t sealed will leak. It’s these leaks that can undermine all of your hard (and expensive) soundproofing efforts.
This means larger openings, like doors and windows, need special care. For the best sound isolation, an airlock consisting of two back-to-back doors is ideal. The door bottoms should have self-actuating bottom gaskets that seal when closed. For windows, you’ll want insulated units with at least one of the panes made of laminated glass.
Most residential walls are constructed using 2-by-4 studs with ½-inch drywall as a finished surface. Think of a wall as a giant speaker. It will have a frequency at which it resonates – acousticians call this the room mode. For a recording environment, resonating walls can muddy the sound of the room. This is especially true of small rooms, because there’s less room for the sound to dissipate.
By simply varying the thickness of standard materials on the walls, we can decrease the chance that resonating materials will be a problem. For example, alternating ½-inchdrywall on one side and ⅝-inch on the other will ensure that the resonant frequencies aren’t the same.
So, now you know a lot about how sound moves and how you can control and contain it, which is great information if you’re designing from the ground up, but many of us don’t have that luxury.
Converting an existing space can essentially be done in two ways. The first is by adding acoustical treatments to an existing room. You can modify the absorption and diffusion fairly easily in this way; even altering the room shape is possible with freestanding panels or objects. This option is most appropriate for renters, because it’s less permanent. However, it’s also less successful, because acoustically isolating a space is a difficult and more intrusive process.
Open framing in a garage is actually acoustically quite nice, but an uninsulated garage can make for some tense neighborly relations. By adopting the room-within-a-room approach, you’ll greatly reduce the amount of sound transmitted to the outdoors in a garage space. This interior room lining can be constructed using relatively inexpensive off-the-shelf materials if the concepts discussed are followed. Isolate first, then balance absorption and reflection.