Game Development Reference
ever, in order to create realistic sounds that lend themselves to creating an immersive
environment, complimenting immersive visuals and in-game behaviors, we need to
understand the physics of sound, how we perceive it, and what sound tells us about its
source and the environment.
Given that this is a book on game physics, we're going to take a fundamental view of
sound, which is that sound is what our brain perceives as our ears sense density and
pressure fluctuations in the air surrounding us. These density and pressure fluctuations
are waves, and as such we'll refer to sound waves . Let's take a closer look.
If a compressible medium experiences a pressure change—say, due to a driven piston
—its volume will change and thus its density will change. In the case of a driven piston,
the region directly in front of the piston will experience the compression first, resulting
in a region of increased density and increased pressure. This is called condensation . For
sound, you can think of that piston as the cone of a loudspeaker. That region of increased
density and pressure will propagate through the medium, traveling at the speed of sound
in that given medium. Figure 26-1 illustrates this concept.
Figure 26-1. Driven piston and loudspeaker analogue
Figure 26-1 (a) illustrates the driven piston concept, while Figure 26-1 (b) illustrates the
loudspeaker analogue. As the piston or cone displaces fluid (say, air), causing compres‐
sion, and then withdraws, a single high-pressure region followed by a low-pressure
region will be created. The low-pressure region resulting from withdrawal of the piston