or audition : the subjective response to sound, including the entire mechanism of the outer, middle, and internal ear, and the nervous and cerebral processes which translate the sound into meaningful signals; the sense of sound perception from tiny hair fibers in the inner ear detecting the motion of a membrane which vibrates in response to changes in the pressure exerted by air molecules, within a frequency range (at best) of 20 to 20000 Hz, though this varies significantly with age, occupational hearing damage, and gender. Sound can also be detected as vibrations conducted through the body by tactition, including frequencies lower and higher than ear range. Human ear is not equally sensitive to all the frequencies of sound within the entire spectrum: middle ‘A‘and its higher harmonics (from 2 to 4 kHz) are at maximum human sensitivity. On sound pressure scale, the normal range of human hearing extends from about 0 dB (threshold of hearing) to about 140 dB; threshold of pain is about135 dB. heuristic : serving to indicate or point out; stimulating interest as a means of furthering investigation.