Acoustics are incredibly important in a recording studio--more important, even, than the equipment used to record the track on. Yet many people allocate only a tiny portion of their budget to acoustic treatments when starting a home studio. By choosing the right type of room, testing the acoustics in that room and setting aside a significant portion of budget for acoustic treatments, people can save a lot of money and aggravation in the long run. Listen to tracks recorded in the studio. if there is an echo or reverb on the track, or if the sound is rather flat, it is because you do not have the correct acoustic treatment in your studio. External interferences, such as the noise of neighbors, are due to insufficient sound isolation.
A common mistake people make is spending too much money on equipment and too little on acoustics. "People think that they are going to be able to overcome acoustics with equipment, and you just can't," Russ Berger, president of acoustic and audiovisual consultancy firm, Russ Berger Design, told Carolin Heinz in an article for the website Electronic Musician. Another common mistake, according to Berger, is to confuse "sound isolation" with the acoustic performance in a room. Sound isolation is simply the process of stopping sound entering or leaving the room. It has no bearing on how sound is absorbed and diffused in the room itself, which are the key determinants of how a recorded track sounds when listened to.
The three main acoustic treatments used are: absorption, diffusion and bass management. As former studio musician and acoustic engineer Ethan Winer explains in his essay, "Acoustic Treatment and Design for Recording Studios and Listening Rooms," "Diffusors are used to reduce or eliminate repetitive echoes that occur in rooms having parallel walls and a flat ceiling... Absorption reduces a room's reverb time. This makes the sound clearer and lets you hear better what is in the recording by minimizing the room's contribution."
A low-frequency absorber is known as a bass-trap, used to flatten the frequency response in the bass range.
The cheapest and simplest type of diffusor is attaching a couple of sheets of plywood to a wall at a slight angle. This prevents sound from bouncing repeatedly between the two walls. Alternatively, you can buy diffusion panels. These are designed with an uneven surface, so that the sound waves are broken up into smaller diffused-sound energy fields. Depending on which type of diffuser panel you buy, it can make the studio sound larger or smaller. The best mid- and high-range frequency absorber is fiberglass. Winer recommends buying sheets 2 feet by 4 feet, and at least 2 inches thick, and attaching them to the walls of the studio. Fiberglass will absorb unnecessary sound and improve the acoustics of the studio. When putting up absorbers and diffusers it is best to cover the entire wall that you want to manipulate. A key area of concern, however, is the first reflection point. Heinz describes this as "the point on the walls and the ceiling that directly reflects your monitors' sound back to your ears." And how do you find it? "Sit in the mix position, and have somebody walk back and forth along the walls on your left and right while holding a large mirror flat against the wall. The points on each wall at which you see the speaker face in the mirror are the first-reflection points."
Square rooms tend to lead to more acoustic problems because of parallel walls. It is best to avoid using a square room for a recording studio, if possible. Although sound isolation is separate from acoustic treatment, it is also integral to ensuring you get a decent recording. Using mass to stop sound entering or leaving the room is one method: cement walls or brick walls filled with sand are good ways of doing this, and act as low-frequency bass traps also. The most effective method of sound isolation is to create a "floating room." A raised floor, with soundproofing mat underneath, and two or three layers of plasterboard on the walls and ceiling create a room within a room. This is expensive to do, however. Other sound-isolation ideas include double glazing on the windows and investing in a heavy fire door.