An echo chamber is a hollow enclosure used to produce reverberation, usually for recording purposes. A traditional echo chamber is covered in highly acoustically reflective surfaces. By using directional microphones pointed away from the speakers, echo capture is maximized. Some portions of the room can be moved to vary the room's decay time. Nowadays, effects units are more widely used to create such effects, but echo chambers are still used today, such as the famous echo chambers at Capitol Studios.
Echo chamber of the Dresden University of Technology
Hamilton Mausoleum has a long-lasting unplanned echo
The Roland RE-501 is an audio effects device capable of creating echo, chorus, reverb and sound on sound type effects
Maxon DE-01 digital echo sound effect pedal
Reverberation, in acoustics, is a persistence of sound after it is produced. Reverberation is created when a sound or signal is reflected. This causes numerous reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture, people, and air. This is most noticeable when the sound source stops but the reflections continue, their amplitude decreasing, until zero is reached.
Automatically determining T20 value - 5dB trigger - 20dB measurement - 10dB headroom to noise floor.