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

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

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

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)

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

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

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

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

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?