What is sound and How is sound produced?

Sound is a physical entity, unlike noise which is the perception of sound. Sound is an high pressure wave front through a medium (such as air, or a liquid such as water, or a solid), wherein the wave front is followed by a reciprocal pressure differential behind it. Sound is produced when something disturbs the medium and sets in motion the molecules in the medium. Frequently, (no pun intended) the wave front/reciprocal entity occurs as an oscillating wave, wherein there are a series of wave fronts (peaks in pressure), followed by wave valleys (lower pressure). The relative height of the peak translates to how much energy is in the wave (how great is the pressure), and the closeness of peak to peak (spatially and temporally) indicates the pitch. Noise, is not a physical entity, but is the mental perception of the physiological response to sound. A wave front is converted from mechanical energy in our ear into an electrical impulse in the brain that analyzes the wave information. The interpretation of the wave front is subjective and the brain may interpret the wave signature as speech, music, clapping, gunshot, hum, etc.