One of the most common ways an audio signal can be processed is by changing its amplitude.
Amplitude conceptually represents the strength of a signal. It is the force sound exerts on an environment. It is the level of sound pressure.
A signal’s amplitude is related to whether it is perceived as being loud or quiet. Therefore, this is an obvious characteristic of a signal to want to process.
You have likely had an experience using some sort of volume knob or volume slider. In essence, this control allows you to change the amplitude of a signal.
If you working with digital audio, a signal’s amplitude can be changed by multiplying each sample by a gain factor.
In this section, I will demonstrate several common ways of processing a signal’s amplitude, starting with a linear gain change.