Technical knowledge and principle of "four-dimensional holography"

Nowadays, although the traditional playback technique based on the channel has excellent performance in both sound color and dynamic restoration, the localization problem of the sound image in 360 degrees space is difficult to achieve a perfect location and accurate restoration because of the limitation of the playback system. However, the presentation of WFS wave field composition skills can improve the positioning of sound to a very accurate situation, thus dealing with this key difficult problem. According to the principle of wave field composition technique, the sound system composed of "four-dimensional holographic sound" (3D Sound) will not only overcome this problem, but also bring revolutionary, natural and seemingly "touchable" ultimate holographic hearing experience.

Wave field composition skills

What is wave field composition?

Wave Field Synthesis (WFS) is a new sound playback skill.

The distribution of sound waves in space is called wave field. The wave field is made up of loudspeaker array, and the 3D algorithm of WFS can form an arbitrary time wave field. That is to say, through the wave field composition of the sound playback, the entire sound field is accurately composed of the dispersion, which is different from the field of psychoacoustics virtual sound image. The concept was first unveiled in 1988 by Professor A.J. Berkhout, the authority on acoustics and Seismology at the Delft University of Science and Technology (T.U.D.) in the Netherlands, and his team.

Huygens principle

The principle of wave-field composition skills is derived from the "Huygens Principle" proposed by Christian Huygens (1629-1695), a Dutch physicist, in 1678.

The Huygens principle states that all points in the arbitrary wavefront in the air can be regarded as new wavelet sources, and the envelope of the wavefront emitted by these wavelet sources at any time thereafter is the new wavefront of the sound wave at that time.

If depicted by sound waves, as shown in Fig. 1, a violin announces a divergent sound wave in which a random wave front can be regarded as composed of numerous wavelet sources, which scatter to announce a new wave front, the envelope of all wavelet sources at any time is the new wave front of the violin sound wave at this time.

Wave field composition is the use of "Huygens Principle", the use of loudspeaker array instead of the wavelet source on the wavefront, through the WFS algorithm, the formation of sound wave dispersion. As shown in Figure 2, two violins play together, and each violin produces its own independent sound wave dispersion. This generalized sound wave dispersion (wave field) can be processed by a loudspeaker array, real-time by the WFS algorithm, broadcasting the information of the wavelet wave source, and composing the result.



Fig. 1: Huygens' principle



Fig. 2: wave field composition

Four-dimensional hologram

To sum up, Ferdimanson planned a set of four-dimensional space sound system, called "four-dimensional holographic sound", according to the wave field composition skills. First of all, the playback of the WFS wave field makes the wave field characteristics of the real sound source thoroughly manifested, because the sound wave dispersion is actually composed of the wavelet source composed of the loudspeaker array. Secondly, this "holographic sound" system, through the playback of the array speakers, further completes the "holographic" positioning of sound, that is, there is no "emperor's position" in the listening area, so that sound can be accurately imaged in the "four-dimensional space" of "three-dimensional (3D) + time axis" instead of just staying in the plane, and finally reproduces the natural and real sound field environment. It gives people a seemingly "hands-on" acoustical experience, and then achieves such as stereo, 5.1 channel and according to the channel surround sound and other traditional methods can not complete the role of sound.

In other words, the skill completes the "sound and image points" in the listening area can be arbitrarily located in the "stable position" in space; together, the sound heard by the listener can also be "stable direction"; in addition, the skill can also complete the "sound path" within the arbitrary listening space movement.

From mono to stereo, to surround sound, each stage is a break in the sound profession, and "four-dimensional holography" will lead to sound, audio profession completed the next round of "innovative" break.