"Hearing people tend to perceive vibrations or sound: thus a very low C (below the bottom of the piano scale) might be heard as a low C or a toneless fluttering of sixteen vibrations per second. An octave below this, we would hear only fluttering; an octave above this (thirty-two vibrations a second), we would hear a low note with no fluttering. The perception of "tone" within the hearing range is a sort of synthetic judgment or construct of the normal auditory system (see Helmholtz's The Sensations of Tone, first published in 1862)."