Acoustic Foam — A specific type of open-celled expanded polyurethane foam that allows sound waves to enter and flow through the foam, absorbing their energy and preventing them being reflected. The density and depth of the foam affects the frequency range over which it is effective as an absorber.
Acoustic Treatment — A generic term embracing a range of products or constructions intended to absorb, diffuse or reflect sound waves in a controlled manner, with the intention of bestowing a room with an acceptable reverberation time and overall sound character.
Bass Trap — A special type of acoustic absorber which is optimized to absorb low frequency sound waves.
Boundary — A physical obstruction to sound waves, such as a wall, or a large solid object. When sound waves reach a boundary they create a high pressure area at the surface.
Decoupler (also isolator) — A device intended to prevent the transmission of physical vibration over a specific frequency range, such as a rubber or foam block.
Early Reflections — The initial sound reflections from walls, floors and ceilings following a sound created in an acoustically reflective environment.
Fidelity — The accuracy or precision of a reproduced acoustic sound wave when compared to the electrical input signal.
Flutter Echoes — Short time-span sound echoes which can be created when sound waves bounce between opposite walls in a small or moderately sized room. A shorter version of the ‘slapback’ echo whch can be experienced in a larger hall when sound from a stage is reflected strongly from the rear wall.
Isolation Room — A separate room or enclosure designed to provide acoustic isolation from external noise. Often used alongside a studio's main live room to record vocals or drums, for example, without spill from other instruments.
Isolator (also decoupler) — A device intended to prevent the transmission of physical vibrations over a specific frequency range, such as a rubber or foam block. The term can also be applied to audio isolation transformers, used to provide galvanic isolation between the source and destination, thus avoiding ground loops.