Stereophony is a multi-channel reproduction technique for audio. Stereophonic perception is based on sum localization and can be manipulated by signal propagation times and level differences so that the listener perceives a virtual sound source between the two speakers. The width of the virtual source depends on the information content of both channels. If this is relatively equal, then a point source is formed between the two loudspeakers; if the two audio signals differ greatly, then a wider sound source is formed.
The stereophonic reproduction
For stereophonic reproduction, two sound sources are used, which are controlled by separate recording, amplification and transmission devices. Stereophonic reproduction is used to generate directional information that is used to recreate the sound of a room.
Stereophonic systems try to come close to the human hearing sensation by emitting directional sound information to the two sound sources via two separate transmission paths. In the playback room, a three-dimensional sound image is then present, which makes it possible to locate individual instruments or speakers.
Simple stereo technology (2.0) has two sound channels and two loudspeakers for the left and right channels. The 2.0 stands for 2 full sound channels and no low frequency channel. In addition to normal stereo, there is also joint stereo, which is more compressed because only certain frequency components of both channels are taken into account.
In general, stereophony is distinguished between time-of-flight stereophony and intensity stereophony. The differences can be seen in the stereo recording technique and the arrangement of the microphones. In time-of-flight stereophony, the two microphones are arranged at different distances and at different angles to each other and can also have different directional characteristics. With these arrangements, one uses the propagation times and level differences to achieve an optimal sound image for stereophonic surround sound. AB stereophony is a recording method that uses delay differences.
In contrast, intensity ster eophony relies on different sound levels impinging on the microphones. In this technique, the microphones are close together or even housed in a single enclosure. Intensity stereophony includes M/S stereophony, XY stereophony, and the Blumlein method. The latter works with two microphones with figure-eight polar patterns that have an angle of 90 degrees to each other.
Another recording technique is separator stereophony. Here, two small- diaphragm microphones are attached to the sides of a separator body as if they were in place of the ears, and the separator body represents the human head. A similar technique is artificial head stereophony, in which the microphones are placed in an artificial head where the ears are located in humans.
If stereophonic recordings are made with more than two microphones, this is called polymicrophony.