An Ode to Stereophonic Sound

Stereophonic sound or, more commonly, stereo, is a method of sound reproduction that creates an illusion of directionality and audible perspective. This is usually achieved by using two or more independent audio channels through a configuration of two or more loudspeakers in such a way as to create the impression of sound heard from various directions, as in natural hearing. Thus the term “stereophonic” applies to so-called “quadraphonic” and “surround-sound” systems as well as the more common two-channel, two-speaker systems. It is often contrasted with monophonic, or “mono” sound, where audio is in the form of one channel, often centered in the sound field. Stereo sound is now common in entertainment systems such as broadcast radio and TV, recorded music and the cinema.

How It Works

Stereo sound systems can be divided into two forms: The first is “true” or “natural” stereo in which a live sound is captured, with any natural reverberation or ambience present, by an array of microphones. The signal is then reproduced over multiple loudspeakers to recreate, as closely as possible, the live sound.

Secondly “artificial” or “pan-pot” stereo, in which a single-channel (mono) sound is reproduced over multiple loudspeakers. By varying the relative amplitude of the signal sent to each speaker an artificial direction can be suggested. The control which is used to vary this relative amplitude of the signal is known as a “pan-pot”. By combining multiple “pan-potted” mono signals together, a complete, yet entirely artificial, sound field can be created.

Stereophonic sound attempts to create an illusion of location for various sound sources within the original recording.

Continue reading →