Finally, the speakers and microphones themselves can cause non-ideality in the
channel. The transducers found in speakers and microphones convert the electrical signal
into a mechanical sound pressure signal and back. These transducers are imperfect in this
conversion, and therefore there is typically some amount of error introduced by the
speaker when it converts the electrical signal to sound pressure waves, and by the
microphone when it converts these waves back into an electrical signal. This error can
cause signal distortion at specific frequencies adding to the channels non-ideality.