Just like large big commercial studios, smaller and home studios suffer from acoustical interference that can make it more difficult to mix, especially when surrounded with the sound effects and ambiance that now typifies today’s stereo and 5.1 surround sound mixes. In professional studios, the walls are strategically treated with fabric-covered absorptive panels on the sides, front, rear and sometimes on the ceilings.
The key to improving intelligibility (or our ability to discern what we want to hear and what we do not) is achieved by reducing unwanted reflections from hard wall surfaces.
What happens is that the direct sound from the loudspeaker arrives at the listening position first and then the reflected sound arrives a few milliseconds later. These loud reflections cause the brain (human hearing mechanism) to have to ignore the second sound, thus making us work hard for nothing. In the studio, this effect is known to contribute to listening fatigue.
The solution can actually be quite simple.
Sound, especially in the voice range, is directional. This means that by using simple vectors, you can strategically position acoustic panels where they will be most effective.
By sitting in the various listening positions and simply moving a mirror on the wall to mark the areas where you see the speaker in the mirror, you will establish the ideal locations on which to position your panels.
The most common surfaces to treat a project studio is on the side walls in between the reference monitors and the listening area. These are usually positioned waist-high to control the upper section of the wall, which will be most prone to reflections. By leaving some open space on the wall, you retain some of the natural ambiance of the room, which will yield a more natural sound.
Treating either the receive wall or the transmit wall (behind the loudspeakers) will also help eliminate flutter echo and standing waves that can further deteriorate the sound. This is particularly helpful in square and rectangular shaped rooms where the parallel surfaces work in tandem to cause long trailing echoes.