1. What is stereophony?
Stereos = solid (having dimensions: length width, height)
Phonics = study of sound
stereophony (stereo) is an aural illusion – a trick that plays on your perception of sounds in a three-dimensional space.
Generally thought of as a 2-speaker sound reproduction system, though this does not necessarily have to be the case

2. How you hear stuff in the real world
Localization
Review of intensity
Review of phase
Review of polarity

3. Monophonic sound 1 signal; 1 transmission channel
Simplest example is 1 microphone → 1 speaker
Cannot convey a sense of “width” (left to right)
Can only convey limited impression of front to back of sound stage

4. Stereophonic Sound Requires 2 signals; 2 transmission paths; 2 ears
“Stereo does not equal mono times two”
Randy Hoffner, NBC
Must have some “minutely differing cues”
must have correlation between 2 signals
Slight differences in intensity (level)
Slight differences in phase (time)

5. Stereo Imaging Interchannel differences generate interaural cues
In real life: single source reaches both ears
In stereo: two sources reach both ears

6. A bit about Binaural Stereophony relies on “crosstalk”
BOTH Loudspeakers are heard by BOTH ears
In Binaural - No Crosstalk!
Signal for right channel reaches right ear only
Signal for left channel reaches left ear only
Headphones are binaural
True 3D sound is possible with headphones
More on this later

7. Perceptual Space Cocktail Party effect
Elements of signal with high degree of coherence and correlation will separate perceptually from those without
Total coherence and correlation = localize in center of head
Total incoherence = split or no image; localizes at extreme left or right

8. Stuff to do Listening examples Intensity panning Delay panning
Polarity flip
Correlation meter
Mono button
Binaural unmasking

9. We can conclude In a stereophonic or binaural system:
Signals with total phase coherence will localize in the center
Signals with a lack of sufficient coherence or correlation will “split apart” or not make a coherent stereo image
How many dB to shift a signal all the way to one side?
How many milliseconds to shift a signal all the way to one side?