"Stereo" recordings are essentially any recording made with
two channels of audio, where the signal on each channel is different.
In contrast, "dual mono" is also two channels of audio, but
where the signal on each channel is the same. Either of these recordings
can be made with Omnidirectional (sometimes called binaural) or Unidirectional
(sometimes called Cardioid) microphones.
In a stereo recording, when you record something with two microphones
spaced some reasonable distance apart, you get slightly different sound
waves hitting each mic, resulting in different sounds recorded in each
channel. When you play the recording back, you hear a sense of space
between the speakers (or headphones) which creates the stereo image.
"Binaural" recordings are two channel recordings created
by placing two omnidirectional microphones inside, or as close to the
ears as is practical. Using this technique, the head and ear structure
affect the way sound waves are picked up by the microphones so that
the location information contained in the frequency, amplitude and phase
responses of the left and right channels closely match the cues required
by the human auditory system to localize sound sources. Positioned in
this way, the microphones accurately capture sonic information coming
from all directions and will produce extremely realistic recordings
when listened to through headphones.
If you have any questions regarding this topic, please contact