The brain is so attuned to the overtone series that if we encounter a sound that has all of the components except the fundamental, the brain fills it in for us in a phenomenon called restoration of the missing fundamental. A sound composed of energy at 100 Hz, 200 Hz, 300 Hz, 400 Hz, and 500 Hz is perceived as having a pitch of 100 Hz, its fundamental frequency. But if we artificially create a sound with energy at 200 Hz, 300 Hz, 400 Hz, and 500 Hz (leaving off the fundamental), we still perceive it as having a pitch of 100 Hz.
