It refers to the sound with three-dimensional sense. The sound emitted by nature is stereo, but if we record and amplify these stereos before releasing them, all the sounds are released from a speaker, and this reproduction (relative to the original sound source) is not stereo. At this time, because all kinds of sounds are emitted from the same speaker, the original sense of space (especially the sense of spatial distribution of sound groups) has disappeared. This playback is called mono. If the whole system from recording to playback can restore the original sense of space to a certain extent (complete restoration is impossible), then this reproduction with a certain degree of spatial distribution characteristics such as azimuth level is called stereo in sound technology.

Second, joint stereo.

Joint stereo mode is one of the stereo modes of audio coding. The joint stereo mode makes full use of the similarity of the left and right channels, and does not encode the same part of the left and right channels repeatedly, thus reducing the waste of data, thus displaying more details at a lower bit rate. For audio with little difference between left and right channels, joint stereo coding mode can usually achieve better results at low bit rate. Joint stereo is to make the same part of the left and right channels into one channel (L/2+R/2) and the different parts into one channel (L-R). In this way, when the left and right signals are the same, L-R has no coded output.

Third, in short, the joint stereo is the result of further optimization on the basis of stereo, which is more connotative and expressive than the stereo on the same basis.