Sheer Silence
this was the brand name of Audio Performance Incorporated's disruption bubble generator. This device created a two-meter sphere which did not allow sound waves to penetrate it. Thus, beings inside the Sheer Silence bubble could converse without fear of being overheard. The Sheer Silence was originally marketed to beings who wanted to enjoy music or a conversation in a semi-public area, creating a personal "listening chamber." However, criminals and spies soon discovered that the Sheer Silence provided an added emasure of security for clandestine communications.