Adding Sound - Game Development with SlimDX - page 83

The basics of sound
Before we get into our sound programming, let's cover the basics of sound. We need
to have a basic understanding of sound before we start doing our sound program-
ming.
Sound is composed of waves. A sound wave is essentially just a pressure wave trav-
eling through the air. When it hits your eardrum, a signal is then sent to the brain
telling it about the sound wave that hit it. The brain converts this information into what
we think of as a sound.
One of the most common attributes we give to sounds is the idea of volume . So what
exactly is volume? Simply put, it is the amplitude of the sound waves. If you think of a
drawing of a wave, the height of a wave is its amplitude. In other words, amplitude is
how big the wave is. Look at the following diagram to see this:
The amplitude or volume of a sound wave
Another very important attribute of sound is the idea of frequency . So, on a drawing
of a wave, its wavelength is simply how wide the wave is, and the length of the waves
determines their frequency. Frequency refers to how often the waves hit, rather than
to the length of a single wave. The higher the frequency of the sound waves, the high-
er the pitch of the sound is. Likewise, lower frequency sounds have a lower pitch.
The term pitch of course refers to how high or low a sound is. The following diagram
shows the concept of frequency:
The wavelength or frequency of a sound wave
Frequency is measured in Hertz ( Hz ). The term Hertz generally means cycles per
second. So if we have a sound that is at 100 Hz, this means that 100 sound waves
hit our eardrums per second. The unit Hertz can be applied to any event that hap-