Whether you're monitoring or recording audio, the room in which tasks are being carried out is absolutely crucial to the response from the system and microphones. Absorptive and diffusive materials, along with the minimization of external noise such as dilution and pollution, all play a vital role in the quality and “true-ness” of acoustic audio. These methods will drastically make a positive difference but there are some things you need to avoid in the general construction and design of a room, and its relative dimensions and angles.
The action and phenomenon of sound, is very much alike that of light. Sound can reflect off smooth surfaces like light can reflect off mirrors, sound can also be absorbed or diffused off of irregular surfaces like light can absorb into darker surfaces. Thinking about sound in this translated way can help further rectify acoustic problems.
When sound is projected and reflected at particular angles, they can overlap and sum in such a way that causes either a partial loss in energy, a partial sum in energy, a complete loss in energy or a complete sum in energy. The summing of energy is referred to as nodes where one particular location in a room will experience a higher than projected sound pressure level. The loss of energy is referred to as inter-nodes where one particular location in a room will experience a lower than projected sound pressure level.
The location of these standing waves and absent sound pressures depends largely on the relationship of the dimension and angles of a room to a frequency. Different frequencies have different wavelengths meaning the positive and negative pressures of a wave will vary in physical length. Low frequencies have large wavelengths while higher frequencies have far shorter wavelengths.
If a wavelength fits perfectly (from the start of cycle to the end of the cycle) within a room. That frequency will become trapped and ultimately will cause summing and cancelling at various locations of the room. This is referred to as a standing wave, where nodes and internodes are the existent. At the crest and troughs of a wave, you will notice an abundance of sound pressure whereas the internodes (the beginning, middle and end of a wave) will cause total cancellation where you will experience a loss in sound pressure.
Ultimately, the size of a room will always resonate a particular frequency based upon physical dimensions. Thus, the goal is not to eliminate this but to minimize the potential for it. Using just two walls in this previous example, is never the case in a studio control room. You will have 3 different potentials for standing waves; front to back, left to right, top to bottom.
If a frequency gets trapped between a defined distance, it is highly recommended that the distance between those to reflected walls; front to back, left to right, or top to bottom, is not mimicked on any other pair of surfaces. This will double your problem with that frequency.
Think about a cubed room at 10 feet between all 3 opposite surfaces. 112Hz will become trapped 3 times causing an extreme problem at that frequency. Thus, this room type is absolutely the wrong decision when designing a space for recording or monitoring. A 12’ x 12’ x 12’ room is bad while a 10’ x 13’ x 17’ room will not create a double or triple build up at a particular frequency. Granted there are 3 standing wave potentials but that is always to be expected.
Often, when researching or simply observing a studio floor and control room setup, you will notice very odd angles, never (or very rarely) will you see perfectly adjacent walls as this increases potential for standing waves. Simply by angling walls away from one another will cause the sound to be deflected in a slightly different direction removing the potential for a problem.
Choosing dimensions that are not as easily mathematically compatible, and angles that favour deflection at non-adjcent angles is the greatest starting point in achieving an ideal room.