CAKEWALK sonar x3, Reference Manual

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823
Digital audio fundamentals
Editing audio
Example—a guitar string
To understand the process better, let's take a closer look at a guitar string.
When a finger picks a guitar string, the entire string starts to move back and forth at a certain rate.
This rate is called the
frequency of the vibration. Because a single back and forth motion is called a
cycle , we use a measure of frequency called cycles per second , or cps . This measure is also
known as Hertz , abbreviated Hz . Often the frequency of vibration of an object is very fast, so we can
also express the frequency in thousands of cycles per second, or kilohertz (abbreviated kHz )
The actual distance the string moves is called its displacement . This is proportional to how hard the
string is plucked. A greater displacement results in a louder sound.
The displacement of the string changes as the string vibrates, as shown here:
The segment marked “A” represents the string as it is pulled back by the pick; “B” shows it moving
back towards its resting point, “C” represents the string moving through the resting point and onward
to its outer limit; then “D” has it moving back towards the point of rest. This pattern repeats
continuously until the friction of the molecules in the air gradually slows the string to a stop. As the
string vibrates, it causes the molecules of air around it to vibrate as well. The vibrations are passed
along through the air as
sound waves . When the vibrations enter your ear, they make your eardrum
vibrate, and you hear a sound. Likewise, if the vibrating air hits a microphone, it causes the
microphone to vibrate and send out electrical signals.
In order for us humans to hear the sound, the frequency of the vibration must be at least 20 Hz. The
highest frequency sound we can hear is theoretically 20 kHz, but, in reality, it's probably closer to 15
or 17 kHz. Other animals, and microphones, have different hearing ranges.
If the simple back-and-forth motion of the string was the only phenomenon involved in creating a
sound, then all stringed instruments would probably sound much the same. We know this is not true,