The answer is "a hammer hitting a metal cup".
Sound is delivered when something vibrates. Sound waves are formed when a vibrating object makes the encompassing medium vibrate. A medium is a material in which a wave goes through. As sound waves travel through a medium the particles vibrate advances and in reverse. A sound's volume, how boisterous or delicate it is, relies upon the sound wave. Vibrations in air are called voyaging longitudinal waves, which we can hear. Sound waves comprise of zones of high and low weight called compressions and rarefactions, separately.