Acoustic materials are used in recording studios, the home and in offices to manipulate, deaden or lessen sound and noise. Noise can be reduced in energy, absorbed to stop resonance and echoes and reduced in pressure level using these materials. If you are constructing your own sound studio, acoustic materials are a necessity to get the best sound recording possible.
Diffusors are used in areas with flat ceilings or parallel walls to stop or reduce sound echoes that can occur. Diffusion can be used in conjunction with absorption to reduce echoes and reflections even more. The cheapest and simplest type of diffuser is created by placing a few sheets of slightly bent plywood to a wall at a small angle. Installers then place fiberglass beneath the plywood to prevent resonating. Professional diffusers have a complex pattern, an irregular surface and different depths to scatter sound waves.
Midrange and high frequency absorbers are acoustic materials that absorb any frequency above 500 hertz. Absorbers, like diffusers, reduce ringing and echoing but they also reduce the reverberation time of a room. Reduced reverb time equals a clearer sound and less contribution from the room itself. If there is too much reverb time, that is echoing and ringing, what sounds right on your system may sound differently on another system. Rigid fiberglass is one of the major materials for absorbing midrange and high frequencies.
Low frequency absorbers are also called bass traps. These acoustic materials reduce the reverb time in larger spaces like churches, auditoriums and large recording studios. They are more frequently used in listening rooms and studios to flatten the bass range and lower modal ringing. Bass traps are also used to reduce standing waves and the acoustic interference that can occur in a small room. When sound waves bounce off walls, the floor and the ceiling, they run into other sound waves which lead to different sound peaks throughout the room. Bass traps prevent this phenomenon. A thicker fiberglass than for the midrange and high frequency absorbers works well as a bass trap, as do bales of fluffy fiberglass in the corner of a room.