Sound is a form of mechanical energy that transmits vibrations through a medium, such as air, solid, or liquid, by creating cyclical variations in pressure known as sound waves. These waves are characterized by two primary physical properties: frequency, which determines the pitch of the sound, and amplitude, which relates to the intensity or loudness. For sound to propagate, a medium must exist, meaning it cannot travel through a vacuum. Biologically, the perception of sound occurs when these pressure waves are received by specialized sensory organs, converting the physical vibrations into electrical signals that are interpreted by the nervous system. The study of sound involves acoustics, which examines both the physical generation and propagation of waves, and psychoacoustics, which investigates how these waves are perceived by living organisms.