" Acousmatic "; sound whose origin is not seen. The listener is not having any visual cue attached. The first recorded use of acousmatic sound was by Pythagoras way back in Ancient Greece. Pythagoras would place a black curtain between him and his audience when giving lectures. He did this so that his students would focus more on his speech than on his person. The word acousmatic comes from the Greek word akousma: what is heard.

Klas Dykhoff, sound editor and professor at Dramatiska Institutet