Sound is a form of energy that causes the sensation of hearing. Sound needs a medium to travel. Sound travels through gases, liquids and solids. The speed of sound is the maximum in solids, less in liquids and the least in gases. Sound cannot travel through vacuum. In humans, sound is produced by the voice box or the Larynx. Vocal cords in the larynx vibrate and produce sound. We hear sound with our ears. The ear drum has a vibrating membrane like a stretched rubber sheet. When a sound note reaches the ear, the ear drum vibrates, and the vibrations get converted into signals that are carried to the brain to get a sensation of hearing.
To produce pleasant sounds, a number of musical instruments have been developed. Some instruments produce sound due to the vibration of membranes, some due to the vibration of strings, and some others produce sound due to the vibration of an air column. The to and fro or back and forth motion of an object is called vibration. The sitar, veena, violin, guitar and ektara are some stringed instruments. The tabla, cymbals, ghatam, kartal and manjira are some instruments that work on the vibration of a membrane, and instruments like the flute and the trumpet produce sound due to the vibration of an air column present in them.