Echo Chamber

An echo chamber is a hollow enclosure used to produce echoing sounds, usually for recording purposes. For example, the producers of a television or radio program might wish to produce the aural illusion that a conversation is taking place in a cave; this effect might be accomplished by playing the recording of the conversation inside an echo chamber, with an accompanying microphone to catch the echoes.

In music, the use of acoustic echo and reverberation effects has taken many forms and dates back many hundreds of years. Medieval and Renaissance sacred music relied heavily on the composers' extensive understanding and use of the complex natural reverberation and echoes inside churches and cathedrals. This early acoustical knowledge informed the design of opera houses and concert halls in the 17th, 18th and 19th centuries; these were deliberately built to create internal echoes in order to enhance and project sound from the stage in the days before electrical amplification. Sometimes echo effects were the unintentional side effect of the architectural or engineering design, such as for the Hamilton Mausoleum in Scotland, reportedly having the longest echo of any building.