The "22.2 multichannel sound system"
The measurement of the head-related transfer function
The headphone processor that supports 22.2 multichannel sound
The existing microphone array, which is composed of multiple microphones
Japan Broadcasting Corp (NHK) developed a headphone processor that can precisely reproduce "22.2 multichannel sound," which provides more realistic sensations compared with 5.1ch surround sound, with headphones available on the market.
The 22.2 multichannel sound system is a 3D audio reproduction system that NHK has been developing for Super Hi-Vision video. Sounds coming from the front, rear, right, left, above and below can be reproduced in detail by three layers of speakers, with nine channels on top, ten in the middle and three at the bottom, as well as a two-channel LFE (Low Frequency Effects) speaker, according to NHK.
The three-dimensional audio reproduction was realized by inputting the values obtained by measuring the head-related transfer function (HRTF), which indicates how the sounds are transmitted from the speaker to the right and left ears, into the headphone processor in advance, according to NHK.
The HRTF mathematically indicates clues to determining the directions from which sounds are coming, such as differences in volume and time for the sound to reach the right and left ears and changes in tones due to differences in the shapes of heads and ears.
By using the headphone processor, users can listen to recorded 22.2 multichannel sounds in a field pick-up van, where multiple speakers can not be used. Therefore, the processor will improve work efficiency of outdoor filming, NHK said. Previously, a studio equipped with multiple speakers had to be used to precisely listen to sound recorded using the 22.2 multichannel sound system.
NHK also developed a one-point microphone, into which a number of microphones are integrated, for recording 22.2 multichannel sound.
In order to pick up 22.2 multichannel surround sound, sounds coming from every direction have to be recorded. Therefore, many microphones had to be positioned for sound recording, and it was a lot of work to produce live programs.
The one-point microphone developed this time is divided into multiple chambers using sound-insulating plates, with one microphone in each chamber. The one-point microphone, despite its small size, can record 3D sounds because interruption between adjacent microphones is prevented, NHK said.
This microphone makes it possible to broadcast live programs with high mobility from locations where large microphones can not be used, increasing the opportunities to produce Super Hi-Vision contents.
NHK will exhibit the headphone processor and the one-point microphone at the 2009 NAB Show (NAB), which will take place from April 20 to 23, 2009, in Las Vegas.
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