rough a physical medium. This includes ears,
            skin, and also artificial devices such as microphones,
            seismographs, etc. Note: <a
            href="./physiology-vocab.html#Eye">#$Eyes</a> are not <a
            href="./perception-vocab.html#VibrationThroughAMediumSensor">#$VibrationThroughAMediumSensors</a>
            because there need not be any physical medium for
            electromagnetic wave propagation. This is a somewhat close
            call, and indeed in past centuries m