Game Development Reference
In-Depth Information
CHAPTER 26
Sound
In this chapter we'll explore some basic physics of sound and how you can capture 3D
sound effects in games. We'll refer to the OpenAL audio API for some code examples,
but the physics we discuss is independent of any particular API. If you're new to Open‐
AL, it's basically OpenGL for audio. OpenAL uses some very easy-to-understand ab‐
stractions for creating sound effects and handles all the mixing, filters, and 3D synthesis
for you. You basically create sound sources , associate those sources with buffers that store
the sound data, and then manipulate those sources by positioning them and setting their
velocity (among other properties). You can have multiple sources, of course, but there's
only one listener . You do have to set properties of the listener, such as the listener's
position and velocity, in order to properly simulate 3D sound. We'll talk more about
these things throughout the chapter.
What Is Sound?
If you look up the definition of sound online, you'll get answers like sound is a vibration;
a sensation perceived by our brains through stimulation of organs in our inner ear; and
a density or pressure fluctuation, or wave, traveling through a medium. So which is it?
Well, it's all of them, and the interpretation you use depends on the context in which
you're examining sound. For example, noise control engineers aiming to minimize noise
on ships focus on vibrations propagating through the ship's structure, while medical
doctors worry more about the biomechanics of our inner ear and how our brains in‐
terpret the sensations picked up by our ears, and physicists take a fundamental look at
density and pressure fluctuations through compressible materials and how these waves
interact with each other and the environment. We don't mean to suggest that each of
these disciplines views sound only in a single way or context, but what we're saying is
that each discipline often has its own perspective, priorities, and standard language for
the subject. To us, in the context of games, sound is what the player hears through his
speakers or headphones that helps to create an immersive gaming environment. How‐
 
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