Pro Tools 101_ An Introduction to Pro Tools 11 ( PDFDrive )

Tip: The following information provides an overview of the concepts of
digital audio theory. Although you do not need to be an expert in this
material, gaining exposure to these principles now will enrich your
understanding of many of the processes discussed later in the book.
Basic Parameters of Sound: Waveform, Frequency, and Amplitude
To work effectively with sound, it is helpful to understand a bit about what
sound actually is and what gives a sound its character. When we hear a
sound, what we actually experience is a variation in the air pressure around
us. This variation results from vibrations in material objects—whether a
tabletop, a car engine, or a guitar string. When a vibrating object moves
through one complete back-and-forth motion (one cycle), the variation in air
pressure that it produces becomes an auditory event. If the object is vibrating
at a frequency that falls within the range of human hearing, we perceive it as
a sound. The nature of the sound we hear is determined by the waveform,
frequency, and amplitude of the vibration.
Tip: The range of human hearing is between 20 and 20,000 cycles per
second.
Waveform
The waveform of the sound pressure variations that reaches our ears creates
our perception of the sound’s source, be it a knock on a table, a running car
engine, or a plucked guitar string. The waveform is the “shape” of the sound
—or, more accurately, the shape of the vibration that produced the sound. As
a vibrating object moves through its back-and-forth motions, its path is not
smooth and continuous. Instead, the cycles of vibration are typically complex
and jagged, influenced by factors such as the physical material that the object
is composed of and the resonance induced by the object’s surroundings. Each
object vibrates differently; the waveform of the vibration gives the sound its
unique character and tone.
Frequency
The frequency of the sound pressure variations that reaches our ears creates
our perception of the pitch of the sound. We measure this frequency in cycles
per second (CPS), also commonly denoted as Hertz (Hz). These two terms