What is Surround Sound?

Surround sound primitive refers to the full-space stereo perception of the location of a spatial sound source by human hearing. Surround sound has a real sense of audio space. Generally, the so-called stereo is the use of modern electro-acoustic technology to adjust the volume and phase of each frequency component of each group of left and right channel sounds without changing the position of the left and right channel speakers. A psychological "sound image" appears. For surround sound, two additional speakers placed at the back are added, so that each group of sounds has a psychological "sound image" not only on the front, but also in different positions behind it, forming a full three-dimensional sense of space. ^[1]

Stereo recording was introduced in the mid 1950s, and then a stereo playback system emerged. It can be said that the 1960s was the golden age of stereo. At that time, the term "surround sound" did not yet exist in the dictionaries of record companies or audio manufacturers.

But in the field of research, researchers have already had the idea of using the indoor acoustic information of the concert hall to establish realistic stereo effects, and have carried out related experiments. For example, the "surround" system proposed by Case, Steinke and Wagner is to place two or more speakers behind the listener to reproduce the sound field effect, which is very similar to today's surround sound. However, due to technical and equipment limitations, these experimental studies have not been promoted in the market.

In the mid-1960s, the introduction of multitrack tape recorders introduced multichannel recording. The sound engineer can use multiple channels for recording, from the initial 3 channels to the 24 channels, making it possible to independently record the environmental information, which also plays a vital role in the promotion of surround sound systems in the field of music. ^[2]

The surround sound effect is actually a result of delaying the sound for a certain time and mixing it with the original sound without delay, thereby enhancing the sense of weight and charm of the sound. The longer the delay time, the greater the echo space produced. The so-called "residual sound revolves around the beam for three days" means this. Of course, the delay time is too long, and the echo effect is not good, it is usually on the order of tens of milliseconds to more than 100 milliseconds. ^[3]

At present, the application of home multi-channel systems is in a situation where multiple surround sound processing methods coexist, and new and old systems are alternated. In terms of hardware, there are many types of surround sound processors. Adopted

There are many ways to classify surround sound.

According to the applicable source of the program, it can be divided into two categories: one is audio-only surround sound (A surround); the other is audio-visual co-existence surround sound, which is often referred to as audio-visual surround sound (AV surround).

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Surround sound is characterized by a sense of direction, that is, the listener can feel the direction of the sound source; there is also a sense of surround, that is, the listener feels surrounded by the sound source; and a sense of expansion, that is, the sound source diffuses around and is reflected by the object a feeling of. ^[6]

When listening to surround sound works, we find ourselves surrounded by music, as if we were in the same space as the recording. We are no longer bystanders, and even if we cannot participate, we are at least an internal observer (at least in our feelings). Now, listeners can be surrounded by sound (and become part of the recording space), or they can observe a piece of music in 360 ° panorama mode through production methods. Surround sound will have a profound impact on music. In surround sound recording, the localization of sound and the shaping of environmental features will be achieved using a different method than stereo. At the same time, the distance information will also show new characteristics. ^[7]