acousmatic sound is sound that is heard without an originating cause being seen. the word "acousmatic", from the french "acousmatique", is derived from the greek word "akousmatikoi" (ἀκουσματικοί), which referred to probationary pupils of the philosopher pythagoras who were required to sit in absolute silence while they listened to him deliver his lecture from behind a veil or screen to make them better concentrate on his teachings. the term "acousmatique" was first used by the french composer and pioneer of musique concrète pierre schaeffer. in acousmatic art one hears sound from behind a "veil" of loudspeakers, the source cause remaining unseen. more generally, any sound, whether it is natural or manipulated, may be described as acousmatic if the cause of the sound remains unseen. the term has also been used by the french writer and composer michel chion in reference to the use of off-screen sound in film. more recently, in the article "space-form and the acousmatic image" (2007), composer and academic prof. denis smalley has expanded on some of schaeffers' acousmatic concepts.