Virtual Microphones
Multichannel audio can enhance the sense of immersion for a group of listeners by reproducing the sounds that would originate from several directions around the listeners, thus simulating the way we perceive sound. Although there are consumer media that allow the delivery of multiple channels of audio, only a limited set of multichannel music recordings have been made to-date.
We have developed a novel method that derives additional channels from the information contained in just one or two signals (e.g., the left and right signals in a traditional stereo recording). This method is particularly applicable to multichannel rendering of live performances in which it is possible to recreate the signals at several "virtual" microphone locations based on previous knowledge of the acoustical characteristics of the venue. A set of filters at the receiving end processes the signals from a pair of main microphones and synthesizes the signals at the virtual microphones distributed around the room. The result is a multichannel rendering of the performance that significantly increases the realism and sense of listener immersion without imposing additional bandwidth requirements. An extension of this method can be used to convert existing monophonic or stereophonic material to multichannel by filtering the existing sound through a set of filters that contain the acoustical transformations necessary to reproduce sound from various directions.