One common and basic way a signal can be processed is to invert the polarity. Almost all audio mixing consoles have a button on individual channels to invert the polarity of the input signal. Many software plug-ins which perform different kinds of processing, have a button to also invert the signal’s polarity.
Polarity Inversion is a special case of the linear gain gain. In this case, the amplitude of the signal is multiplied by -1. Therefore, the positive values become negative and the negative values become positive.
Next, let’s look at using the addition operator to perform a DC Offset.