EECS20N: Signals and Systems


A system is a function that maps one function space into another. For example, given the function spaces:
  • Sounds = [Time Pressure]
  • Images = [HorizontalSpace × VerticalSpace Intensity 3]
an audio equalizer, which adjusts the tonal balance of an audio signal, is a system:
  • Equalizer: Sounds Sounds.
A room is also such a system. Consider how a cathedral transforms a sound, compared say to an acoustically dead room like one with carpeting all over the walls. In fact, equalizers are often used to correct sounds that are distorted by rooms (the equalizer and room are composed to become one system).