Acoustic materials help minimize sound reflections and acoustic distortion.
When the sound encounters the boundaries of a room, a complex series of reflections occur. It is difficult to isolate the direct sound alone, as the reflections constantly interact to produce a wide range of effects known as acoustical distortion. If proper acoustic design is not utilized, a room will introduce acoustic distortion which prevents us from hearing all of the detailed information the loudspeakers are capable of delivering.
The two primary acoustic materials found in studio environments are absorbers and diffusers.
An absorber is any material that allows air to enter or pass through it.
Most common absorbers include open cell foam, fiber-glass, mineral fiber-wool and acoustic ceiling tiles. The friction of sound energy moving through an absorber transfers sound to heat energy.
Thicker materials offer greater resistance therefore are more efficient in reducing sound and will have better low-end characteristics.
A diffuser is a device that reflects and dissipates sounds. Often they will change the direction and quality of the reflected sound helping reduce slap echo and standing waves.
Sound reflections in a large room can be heard as echoes which may be undesirable since they detract from the direct sound. If the reflection direction is changed by some means, then the walls and ceiling of that environment would no longer make as many reflections, or echoes, and the sound would be uniformly diminishing with time providing a more pleasant direct sound.
Diffusers are usually irregular shaped surfaces set about on the walls and ceiling. In recent years, various acoustical experts have evolved mathematical theories and formulas that have lead to the development of sophisticated diffusers.