Nippon Telegraph and Telephone Corp (NTT) has developed a technology that separates 2-channel stereo sound recorded in a music hall, etc into direct sound and reverberant sound, such as reflected from walls, and creates 5.1-channel surround sound and so forth.
When the new technology, “Revtrina,” is applied to existing stereo sound, it can be converted into surround sound, enabling to, for example, output direct sound from front speakers and reverberant sound from surrounding speakers.
When 2-channel stereo recording is conducted in a music hall, etc, direct sound and reverberant sound are mixed. The new technology checks the correlation between a sound and past sounds, determines whether the sound is direct sound or reverberant sound and separates it.
For each sound, its frequency and time variation of sound volume are compared with those of past sounds. When there is a correlation, it is judged as reverberant sound. And if not, it is judged as direct sound.
Sound recorded in an environment where reverberant sound is generated, such as a music hall, club with live music or theater, can be converted into surround sound by using the Revtrina. The technology can be applied not only to 2-channel stereo sound but also to monaural sound, NTT said.
As a technology to create 5.1-channel surround signals from stereo signals, a method developed by Dolby Laboratories Inc has been widely adopted. According to NTT, Dolby’s method leverages the fact that humans sense a wide soundscope when the correlation between sounds coming to the right and left ears is low. Therefore, Dolby’s technology is totally different from the new technology, which separates reverberant sound to generate surround sound, NTT said.
Tacsystem Inc will show off the software at International Broadcast Equipment Exhibition 2009, which runs from Nov 18, 2009, at Makuhari Messe in Chiba Prefecture, Japan.