Sound travels at different speeds in different materials. Sound always originates from a vibrating object. And something - a medium is required to carry this sound. The medium that sound travels through can be air, water, any object, and so on. Sound cannot travel in a vacuum. Why do you think sound cannot travel where there is no medium? This is because sound travels in waves. The vibrations which produce sound also cause the particles next to them to vibrate. This sets off a chain reaction of vibrations hence the sound wave. Have you ever seen somebody listening intently with his or her ear on railway tracks? What do you think he or she will hear? The person would hear the rumbling noise of an approaching train.

The speed at which sound can travel in different mediums is different. The speed of sound in air at 0 degrees Celsius is 331m/s. As air gets hotter the speed of sound also increases. Sound is able to travel faster in water. In water it travels at 1435 m/s at  0 degrees Celsius. Sound travels fastest in solids. For example in Iron, sound travels at the speed of 5130 m/s at  0 degrees Celsius.

How is Velocity of Sound in Air Measured?

One of the most simple and direct ways of measuring the velocity of sound in air is shown in the picture. Person A stands on a hill with a gun. Person B stands with a stopwatch on another hill at a distance from the Person A in such a way that he can see person A.

Person A fires the gun, Person B sees the flash when the gun is fired and starts his stop watch immediately. When he hears the sound he stops the stop watch.

Knowing the distance between the two persons and the time recorded in the stop watch the velocity of sound in air can be determined.

Measurement of velocity of sound