Game Development Reference
In-Depth Information
Stereo sound
When a sound is played in stereo, it means that the sound has two channels: one
channel is played by the left speaker while the other is played by the right speaker.
This gives a bit of a 3D effect to the sound for the listener. In other words, the sound
is composed of two separate sound tracks, one for each speaker.
This leads us to the concept of a
phase
. You can think of this as referring to how well
the channels in a sound are synced with one another. If the channels are perfectly in
sync, they are said to be
in phase
. Otherwise, they are said to be
out of phase
. So if
you delay one of the channels by a fraction of a second, your sound is out of phase
because the sound from the left and right speakers is not correctly synced with each
other.
There is one last interesting property of sound that we will take a quick look at. It is
directly linked to the concept of a phase. The following diagram shows this:
In the previous figure, we have two sets of sound waves: one is continuous, and the
other is dotted. As you can see, the dotted one is the continuous wave inverted. So
the result is that we have two audio tracks, where one has the opposite phase of the
other. So what happens when we play this sound? Nothing! That's right, absolutely
nothing. Why? Because sound waves with opposite phases will cancel each other
out. In other words, if two sound waves of the same amplitude and frequency coin-
cide with each other, but one of them is inverted, then they cancel each other out. The
second half of the previous diagram shows this. There are no sound waves left since
they canceled each other out, and thus we have silence.
