The goal of properly treating a recording studio is essentially to render the room acoustically isolated and neutral. Sound engineers want to record the best representation of what is being played or spoken, and not have to compensate for poor room acoustics when mixing.
The first step is to soundproof the room isolating it from any airborne or structure borne noise from the outside. This is most efficiently accomplished by decoupling the entire structure of the room with resilient sound isolation clips. Isolation clips are fabricated in a variety of configurations to allow decoupling of walls, floors, and ceilings, thereby interrupting the transmission of sound waves.
Walls and ceilings must also have sufficient mass to block airborne noise. A great way to add additional mass to a wall or ceiling partition and increase its sound blocking properties is by adding a layer of flexible mass loaded vinyl noise barrier and an additional layer of sheetrock. It is also important to seal the perimeter of the partitions and any cabling penetrations with a good silicone or acoustical caulking. Any air leaks will dramatically compromise the effectiveness of a sound barrier.
Doors and windows are typically the weakest links when soundproofing a recording studio. They should be acoustically rated units, (STC 45 and above), with the appropriate seals and hardware. Windows should be constructed of double pane laminated glass with an air gap in between. The pane on the inside of the studio should be installed at a slight angle to diffuse sound waves by preventing them from bouncing directly off of the hard parallel surface of the glass.
The next step is the acoustic treatment of the room itself. Absorption must be added to the walls and ceiling to prevent sound from reflecting back off of the hard parallel surfaces of the room and back to the microphone. One of the most common absorption products used in recording studios are melamine foam panels. These can be similar in appearance but should not be confused with foam egg crate materials used in packaging which do not have the same physical properties or durability of an acoustic panel. A material’s ability to absorb sound is rated in NRC, or Noise Reduction Coefficient. A good sound absorption panel should have an NRC of .80 to 1.15, which means it will absorb 80 to 100 percent of mid to high range sound waves. When choosing an absorber, always check the data sheet for a high NRC and Class A fire rating. Some other excellent absorbers are fabric wrapped fiberglass wall panels, and high performance fiberglass acoustic ceiling tiles.
Low frequencies can be troublesome due to the length and intensity of the sound waves. Low frequencies tend to build up in the corners of the room and cause standing waves which results in a resonant sound in the room. This can be troublesome when recording drums or amps. Low frequency build up can be eliminated by installing acoustic bass traps in the corners of the room. Acoustic bass traps are essentially thick wedge shaped absorbers that are designed to be more efficient in attenuating low end frequencies.