Like many musicians, I’d been playing and recording music in my bedroom or a spare bedroom for as long as I could remember
The obstacles this environment presents to audio recording are apparent to anyone who’s ever tried it: interference from outside noise, disturbing the household and neighborhood peace, limited control over acoustics, and regular encroachment by the rest of the living space. Often the spare bedroom studio is reconfigured for boarding guests, or it gets used as a “temporary” storage space for all those things you and your housemates don’t know what else to do with.
At the same time, the home is exactly the place we would like to perform and record. It’s a comfortable place to be.
Until a few years ago, working in a truly dedicated recording space within the home environment was a fantasy. However, with a little study and a lot of planning I was able to tackle the challenge of building a playing and recording space. Here are some of the constructional details of the project.
Before getting into the design, let’s consider acoustics and construction. The main goals in soundproofing are to prevent unwanted noise from entering into the studio, reduce emissions from the studio to the outside world, and control noise and sound within the studio itself.
Sound control can be thought of in terms of separate high frequency and low frequency components. It’s a simple matter to control high frequency sound. Fiberglass insulation is an excellent absorber of high frequencies. Other absorbing materials such as timber and drywall contribute to the reduction of incoming and outgoing high frequency sound.
Low frequency sound is more troublesome. It can’t be controlled effectively with insulation. Low frequency sound requires significant mass coupled with isolation measures to provide adequate and meaningful reduction.
To provide proper absorption using mass, two or more layers of drywall (a.k.a. sheetrock or gypsum board) or alternating layers of drywall and soundboard are often used. Concrete block construction with spaces completely filled with concrete is also used, and is often coupled with an insulated stud wall covering its surface. The idea is that the more mass there is, the more it is able to absorb and/or dissipate low frequency sound.
Another way to help absorb both low frequency and high frequency sound is to separate two parallel walls with several inches of air. Sound is transmitted through dense objects much more efficiently than through air. The separation of the walls by an air space breaks the physical connection and thus greatly reduces the transmission of sound energy.
This dual wall construction is the strategy I followed. It seemed like the right way to go, and the resulting sound reduction was greater than I’d anticipated. This is a “room-inside-a-room” design, which provides sound isolation by keeping the interior walls and ceiling of the studio space separated from the surrounding exterior walls and ceiling of the garage or living space.
The only common surfaces are the concrete floor and the points of contact between the interior walls and the floor. The interior walls and ceiling are free to move, sway, and vibrate from sound waves without transmitting this energy to the other structural surfaces.
My wife and I had been using our garage as a workspace and storage facility. She is an artist day and night, and I’m a musician and recording engineer by night as the muse favors. We had wanted to insulate and drywall the interior ever since we moved in, but were reluctant because it would reduce the height of the already low ceiling.
But after many years it became clear that we both needed proper workspace. So I created a floor plan (Figure 1) that would allow for the music studio, an artist workspace, and a general workshop area.
Because of the size limitations, I designed a single room studio with the potential to expand into a 2-room (live room/control room) configuration later (of course, my wife will probably be concerned by this small detail when she reads this article). The single room studio can comfortably accommodate three musicians, as long as none of them require a drum kit. The workshop area can be used as an auxiliary recording area as the need arises.
After designing the space, it was immediately evident that my first step would involve dealing with the roof of the existing garage. I was reluctant to replace it, but the low ceiling height (7–81/2 feet) was an issue, and to build a room-inside-a-room the ceiling would have dropped to a suffocating and rather implausible 6 feet at its lowest point.
I decided to replace the conventional roof with a trussed roof designed with extra headroom. If you decide to convert an existing garage into a studio, hopefully you will have more headroom to play with than I did.
The truss design allowed for a large open space, which simplified the construction of walls below. Further, there is security in knowing that all of the engineering, certification and fabrication of the roof trusses are done by the construction yard. With the distinguished help of several family members, we were able to place and secure all the trusses in one day (Photo 1).
The west wall that had previously housed the two garage bay doors had to be completely replaced due to door framing issues, window placements, and termite damage. Prior to construction of the studio room, we insulated all interior walls inside the garage space with R-13 insulation and covered them with 1/2" drywall.
A detail of the dual wall components is shown in Figure 2 (plan view); a diagram of the west interior studio wall is shown in Figure 3. It presents a cross-sectional view of the studio.
Although each and every opening in a studio (doors, windows, cracks, gaps, etc.) compromises the soundproofing, there is some leeway. A door is obligatory, and windows are nice. I wanted natural lighting and elected for two small 1' x 3' windows high on the west wall and one 3' x 3' window facing north. The large window opens, the small ones don’t.
Most local fire codes require at least one sizeable window that opens in each habitable room to provide escape. The high windows on the west wall allow full use of the wall space while letting in daylight.
I was able to obtain soundproof windows on special order from the local Big-Box hardware store. The windows are 1/4" glass on the inside and 1/8" glass on the outside, with the layers separated by a 1/2" gas-filled space.
The four interior studio walls were framed separately on the floor and then leaned into place. These walls were made using standard 2" x 4" stud wall construction with the uprights spaced on 16" centers.
We attached a 3" wide x 1/4" thick strip of rubber to the bottom plate of each wall to provide a modicum of wall to floor isolation. The rubber comes in sheet form; to make the rubber strips, you simply roll up the sheet tightly and cut it with a hack saw at 3" intervals.
We positioned the walls one at a time and bolted them into the concrete floor using wall anchors (Photo 2). It was very important to square up each studio wall and brace them in place temporarily.
With the interior walls trued and secured, it was time to attach the ceiling joists. Using a reference book, we determined that 2" x 6" douglas fir lumber on end and spaced every 16" was sufficient to span the room and support a drywall ceiling.
In Photo 3, taken from inside the studio, you can see the dual wall construction and the attachment of the ceiling joists for the inner room. Despite these well laid plans, I recommend a wall spacing of at least 2", as the 1" separation we used is a little tight, and without caution it may not be enough to keep the interior and exterior wall insulation separated throughout. It also allows a bit of breathing room, since the walls may settle slightly after the room is completed through natural expansion and contraction of the building materials.
I stapled plastic sheeting to the outside of the interior wall to keep the insulation contained within the 31/2" depth of the studs.
Following the stud wall and ceiling joist construction, we installed the electrical and lighting system. If you’re not thoroughly familiar with household electrical circuitry, please hire this part of the job out to a licensed electrician. With exposed walls and a clear plan you will find that the electrical work can be done very quickly by an experienced technician.
Aim to install at least two separate circuits from your breaker: one for the outlets and one for the lights. Although dimmer circuits can be quite appealing, avoid them due to the EM interference they can cause in the line current.
In this studio there are two switched sets of overhead lights (recessed and track) and a bathroom style, low-noise exhaust fan on a single circuit. Another circuit contains eight wall outlets, two per wall. Any additional lighting you may want can always be added using the wall outlets. Although it was harder to work with, we used 12-gauge electrical wire throughout. It can handle a higher load than the 14-gauge wiring found in the lighting and room outlet runs of some homes.
Before insulating and drywalling the interior room I ran a piece of 1" flexible electrical conduit from the middle of one wall of the studio, up and across the ceiling, and down to the middle of the opposing wall. It will house a custom audio and MIDI snake to minimize the clutter of patchcords across the studio floor when bringing in guest musicians and their equipment.
While it’s difficult to foresee future studio configurations and needs, one simple run or two of empty conduit doesn’t cost much and provides an elegant way to expand the studio’s audio and MIDI wiring. During the studio’s first recording session, I tracked a drum kit out in the workshop, and I was kicking myself for not having at least a few XLR inputs available.
Man your caulking guns
In order to ensure the best soundproofing performance, it is critical to identify all potential sources of sound leakage. Any gap or space that air can freely pass through is also a place where sound will enter or exit the room. Small gaps may appear innocuous, but it only takes a few of them to lessen the room’s ability to hold back sound transmission.
Realistically, functional items such as an exhaust fan exit hole and the gap between a moveable windowpane and sash can never be sealed. But a bit of care taken to seal what you can will compensate for the inevitable gaps.
We sealed the window frames with latex adhesive caulk at all points of contact with the framing. The gap between the floor and the interior and exterior studio walls was sealed around the perimeter. Electrical boxes and light fixtures were also sealed where they penetrate the drywall.
The studio door is solid; the hollow-core type normally used for interior doors will transmit too much sound. We outfitted the doorjamb with weather stripping and attached a rubber door sweep to the bottom of the door. An ad-hoc test revealed a noticeable reduction in sound transmission after the weather stripping.
It was somewhat tricky taking care of the drywall detail around the windows. The usual method for finishing window sills is to mount drywall to the faces of the studs that frame the window. But if you’re constructing dual walls for sound isolation, the design philosophy prohibits a hard connection between the inner wall and outer wall.
Our solution was to secure the sill drywall to the window opening of the inner wall and let it float over the studs that frame the window on the outer wall. We glued small pieces of 1/4" foam to the stud faces to help maintain a gap between drywall and the studs of the outer wall. The drywall is free to glide back and forth over the foam when the walls vibrate from sound energy (Photo 4).
We lifted the baseboard off the floor by about 1/8" and screwed it into the wall to prevent it from establishing a hard contact with the floor (Photo 5).
A recording session
Shortly after completing the studio I was asked to record a CD for a local band. This was a great way to put the room through its paces.
We tracked the drums outside the room. The door couldn’t be shut all the way due to the mic cables (remember that conduit I forgot?). Although we used headphones in the studio (control room in this case), there was enough bleed to make balancing the kit mix difficult. I vowed to install a patchbay in the wall of the workshop or a cable tunnel before the next time.
We used a direct box for bass and a mix of a miked amp and direct signal for guitar tracking. The guitar amp was always at a high volume to give the mic a strong signal to bite on. While the guitarist was warming up, a leisurely walk around the building confirmed that sound levels exiting the property were quite civil and easily masked by passing cars. Going back into the studio, I was immediately impressed at the blistering noise within the room and the capacity of the dual wall construction to absorb it.
There’s a vast amount of information on the subject of studio design on the internet. Almost any search will yield hours of worthwhile reading material. There are also general remodeling books for homeowners that provide essential construction know-how.
One book I found useful in designing my studio was Building A Recording Studio by Jeff Cooper (Fifth Edition, 1996 Synergy Group, Inc.). It contains excellent information on acoustical design as well as treatments that can be done to the studio after construction. [Around here we also recommend our pal Dave Moulton’s Total Recording—for this and everything else to do with audio.—Ed.]
While the best possible acoustical environment is always the goal, sometimes you have to accept a certain amount of compromise in the design and building process. Constraints such as the available space, construction expense, construction complexity, and time to completion always come into play.
But when completed, you’ll have created a special space for playing and recording that’s tailored to your needs and lies very close to home. Notwithstanding the practical benefits, it’s a rewarding experience.
John Krikawa is a part-time musician and engineer proudly operating his new studio in central Arizona.