Glossary of Terms
 
  acoustic echo chamber  
  A room designed with very hard, non-parallel surfaces and equipped with a speaker and microphone; dry signals from a mixing console are fed to the speaker, and the microphone will pick up the reverberation of these signals, which can be mixed in with the dry signals.  
  Source: Recording Institute of Detroit  

Also refered as:
  echo chamber
Related terms:
  absorption   echo