Stereo audio refers to the way in which listeners interact with sound. It uses two channels of audio, simulating the difference between the left and right ear in a space.
This helps to create a sense of space in a recording, known as the ‘Stereo Field’. There is a crossover point in the left and right speaker, which accounts for the centre/mono image within this field.
Typically, two microphones on two separate channels/inputs are required to create a stereo recording, as both microphone signals can then be manipulated within the stereo field.
Fun Fact: There is no centre/mono image with earphones/headphones. A psychoacoustic phenomenon occurs where the brain interprets the left and right signals of each speaker and generates a centre image based on its own calculations.
Mono audio is the opposite of Stereo Audio as it only requires a single channel to capture and playback audio.
There is little to no sense of depth within mono recordings. This is due to the lack of the left and right channels, providing only a centre image.
An everyday example of Mono audio is playing your favorite podcast directly from the loudspeaker of your mobile device.
With mono it is impossible to discern a sound existing on the left or right side of the stereo field, from that in the centre.