Free Space Noise Control

The first noise control category of interest here is acoustic radiation into free space. What is acoustic radiation, and what is free space? Acoustic radiation is simply the generation of sound waves by a source. Acoustic radiation is a term commonly used amongst noise control practitioners. The term “free space,” or “free field,” refers to the environment in which the sound source is operating. Free space means that there is nothing to reflect the sound back; it can travel away forever. This is as opposed to acoustic radiation into an enclosed space, like a room. The free space environment is also referred to as “anechoic” (literally, no echo). If you are working in the field of noise control, then you may further subdivide free space into spaces where unreflected acoustic radiation is possible in only some directions, like a “half-space” (for example, if the sound source is sitting on the floor, it can only radiate up, not down). This might also be referred to as “semianechoic.” However, for our purposes of qualitative results examination, we will not be particularly fussed. We will simply assume that the sound can travel away without interference.