Stereo panning
Stereo panning
Panning
Artificially give a spatial position to a signal
Loudspeakers
Crosstalk!
The sound from both speakers reach both ears
At different times
And from different angles
Different HRTFs, ITDs and ILDs
So the sound is reinforced, canceled and filtered in various ways due to crosstalk
Amplitude panning
Different levels on each loudspeaker
Delay panning
Small delay to one of the loudspeakers
Create frequency dependent amplitude differences at the ears
But this dependence is very different to the frequency dependence due to source direction
Panning laws
Panning laws describe the functions to adjust the relative amplitudes between channels
Linear panning
Amplitudes cross in the center at 0.5 amplitude (-6.0 dB)
decibel
(1 tenth of a "Bel")
It's not actually a unit as the units are cancelled!
It's only a ratio
In most practical audio applications, we don't deal with power or intensity but with pressure or voltage, so the formula becomes:
decibel for pressure or voltages
Equal power
Amplitudes intersect at ~0.707 (-3.0 dB)
The amplitudes can be calculated from desired position
Any other curve is possible. Some mixers' panner cross at -4.5dB
Headphones
Since crosstalk is absent on headphones, amplitude panning will produce ILDs and Delay panning will produce ITDs
Interestingly both techniques work on headphones and loudspeakers
But they work differently and this is one of the reasons why panning sounds so different on headphones vs. loudspeakers
