Although there are variations of each, there are two basic types of acoustic treatments: reflectors and diffusers. Each of these acoustic treatments serves a specific purpose for various applications in residential, commercial, and industrial locations. To understand the distinction between reflectors and diffusers, it is important to first understand acoustics and how sound functions in different settings.
Sound is nothing more than vibrations at different frequencies that are picked up and translated by our ears or by recording devices. While the study of sound waves and acoustics can be complex, the easiest way to understand acoustic behavior is by thinking of it as how sound interacts with its environment. The study of acoustics simply describes how a sound reacts as a result of the size, shape, and materials of the space between the sound's source and its destination.
Reflector acoustic treatments help to disperse early reflections, the reverberation that reaches your ears milliseconds after a sound is played. Reflectors are usually made of curved plywood or foam and are specially designed to absorb and redirect mid- to high-frequency sounds. Reflectors are usually installed on the back wall of a space, capturing the high-frequency sounds and redirecting them before the sound waves have a chance to be sent back to your ears.
Diffusers act as an agent to scatter the audio, helping to achieve a more neutral sound space. A diffuser is usually, but not always, made of foam. Most diffusers are designed with a congregated surface to allow for absorption and surface dispersion, much like a radiator diffuses and disperses heat. Diffusers disperse sound waves so a high concentration of a particular frequency fails to exist, leaving the listener with a more evenly balanced acoustic space.
The materials in a room or space have a great effect on how sound is heard. If you took two rooms that were identical in shape and size but differed in building material, you would notice vast changes in the way sound behaved in each. A room made of metal walls would be very reflective, meaning the sound would reverberate off of the walls before reaching your ears. A room made of thick foam would sound dull, because the sound would not have anything off of which to reflect.
In choosing acoustic treatments, it's important to understand your needs. Those needs will vary according to what you are building and whether it is a performance area such as a theater or television studio. Different situations call for different treatments, and understanding that will be of great help in deciding what treatment to use. A basic understanding of sound waves will also help you to make the most out of your space as well as your acoustic treatments.