8 3D Sound Space Capture and Reproduction

  Accurate capture and reproduction of sound space

Amongst realistic sound systems, the 5.1ch surround sound system is the one usually sold. However, it does not faithfully reproduce the captured sound, but uses a human psychological illusion to play back a seamingly realistic sound space. In this laboratory, by faithfully reproducing the captured soundspace, we aim to realize a more realistic acoustic system, and as part of this we are currently studying SENZI and higher order ambisonics.

≪ Classification of 3D Sound Space Capture and Reproduction Systems ≫

Classification Description
Multichannel acoustics
Method reproducing the sound from one direction using a speaker resonating from this direction
(Examples: 5.1ch surround sound,22.2ch multichannel surround sound)
Binaural - transaural recording reproduction
Methods for controlling the sound pressure in the eardrum
(Examples: transfer function synthesis, recording using dummy heads)
Sound field reproduction technology
Method for controlling sound pressure in a specific region
(Examples: wavefront synthesis, higher order ambisonics)

    Humans use only the input from their two ears to estimate the provenance, reverberation or differences in height of sound. This means that reversibly, if you faithfully reproduce the sound coming to your ear , you can make three-dimensional sounds heard with simple equipment such as headphones. SENZI is a microphone array technology made of a high number of microphones installed in an environment you want to record. It transmits the recorded sound information to a remote place and faithfully reproduces this sound's direction, reverberation, height etc. for many listeners. We are currently developing a prototype system that constitutes a spherical microphone array, records sound space using 252 microphones and reproduces the appropriate sound space information corresponding to the head movement of the listener.

      Higher order ambisonics sound space reproduction

    In order to physically reproduce sound space, it is necessary to measure the sound pressure coming from every direction. However, data manipulation then becomes difficult. By using higher order ambisonics, and expressing the captured sound space with a function called spherical harmonic function, it becomes possible to playback sound space with great precision. However, there is a condtion : the speakers must be placed spherically. In this laboratory, we are doing research to realize highly accurate sound space reproduction even with non-spherical speaker arrangements. In addition, to demonstrate this, we have constructed a sound space reproduction system that realizes 4th order ambisonics using 32ch speaker array.

Figure : Higher order ambisonics sound space reproduction

Figure : 32ch sound space reproduction system

Last update: 2017.04.28