Advanced Multichannel Live Sound Reproduction
Progress on immersive presence sound broadcasting
While broadcasting audio has evolved from mono and stereo to 5.1 channel surround sound, its goal has always been to reproduce a sensation of presence similar to being at the site of a broadcast. A sense of presence for sound is created when a listener's sound field (the space where sound waves expand) contains an accurate reproduction of the direction and distance of the sound image, reverberation, and the listener's envelopment, and the sound impression changes appropriately when the listener changes listening locations. Our research on advanced multichannel live sound reproduction has the aim of creating such immersive sound reproduction.
Sound recording and reproduction for advanced multichannel live sound reproduction
The sound we hear consists of a sound component that travels to our ears directly from the sound source (direct sound) and another sound component that reaches our ears after being reflected from obstructions, such as walls (indirect sound). Therefore, the reproduction of sound with a heightened sensation of presence will require the pickup, recording, and transmission of both direct sound and indirect sound, as independently as possible. This will allow the optimum sound field to be composed based on individual reproduction techniques and environments through signal processing on the collected sound data. We employ a technique called high-density recording and reproduction for a sound space; the technique divides the original sound field into small regions with isolated sound pickups in each area. High-density recording and reproduction gives us the ability to reproduce a sound field tailored to a distinct reproduction space.
Advanced multichannel live sound reproduction system
Figure 2 illustrates an advanced multichannel live sound reproduction system that is based on our previous research. This system uses the high-density recording and reproduction technique described above, and we are experimenting with it to record, transmit, and reproduce orchestra performances.
The direct sound from the orchestra's musical instruments, which fill the concert hall's stage, is recorded using a sound-stage capturing system. The sound is reproduced through rows of loudspeakers in front of the audience in the reproduction space. As for indirect sound, a sound space capturing system is installed in the audience seating area to pick up the reflected sound and reverberation in the reproduction space and send them to the loudspeaker arrays. This system naturally reconstructs the sound width and depth of the instruments on the recording stage, and thus it gives the sensation of each instrument's sound being at a specific location. The listener can experience a natural, high-quality perception of presence.
An orchestra performance was presented with this system at various events, including the STRL open house. Listeners had comment such as, "It was highly realistic sound," and "The system allowed me to thoroughly enjoy the music."
We will continue to work toward immersive presence sound broadcasting for the home.
