Sound is vibration. It is created by the movement of a sound source. It travels through air (or another medium) by the movement of air molecules. It is captured with a receiver (a microphone or our ears) by the movement of a diaphragm.
Sound is a signal because there is information in these vibrations. When a person is speaking, vibrations carry the content of the speaker’s message. When a guitar is played, vibrations from the strings carry information about the melody and rhythm of the performance.
There are several important characteristics of these vibrations. The rate at which these vibrations occur is called a signal’s frequency. The strength at which these vibrations occur is called a signal’s amplitude. These concepts will be explored in much greater detail in subsequent posts.
Audio (as a term) is more general than sound. Audio includes signals traveling as sound vibrations, and it also includes various other forms these signals can take.
As an example, a microphone converts a sound signal into an electric signal. The electric signal is still an audio signal, but it is not a sound signal. Audio signals can also take on the form of magnetic particles aligned on analog tape.
For our purposes, we will be primarily working with a digital representation of audio signals. This is a special form of audio based on discrete measurements of a signal.
Next, let’s have a look at how an audio signal can be represented digitally.
Here are some additional links about sound and vibration: