Science Project on “Measuring Distance with Sound”, Project Experiment Topics on Light, Sound, Maths, Optical Illusion for Class 8, 9, 10 and 12 Students.

Measuring Distance with Sound

Materials Required:

1. A large building
2. Measuring tape

The speed of a sound wave is generally fixed at 335 metres per second. When the energy waves actually move, the molecules of the medium it moves through (like metal, water, air) do not travel forward with the wave.

To understand things better, let us return to the example of the wave. When a wave moves in the ocean, the wave itself moves forward, but the molecules of the medium (in this case, water) move up and down with the crest and the trough of the wave.

This explains why a boat hit by a wave goes up and comes down, but does not move forward.

This is the same phenomenon also for a sound wave. The molecules in the air move along with the crest and the trough of the wave, but they themselves hardly move forward or backward.

You must have entered an empty room and heard your own echo reverberate through the room. When your brain hears sounds that are about 1/10th of a second apart, it interprets them, as two different sounds.

Traveling at 1100 feet per second, a sound wave takes 1/10th of a second to cover a distance of around 110 feet.

If you stand before a wall and yell, the sound wave will travel 110 feet and return to you.

This means that you are standing at a distance of 55 feet from the wall. It is quite evident here, that sound waves can be easily used to measure distance.

To be absolutely accurate in your understanding, stand next to a large wall at a distance of 30 feet. Keep yelling your name and keep walking back a little bit, till the time you can hear your echo.

Standing at that spot, mark the distance between you and the wall. The distance now should be 55 feet.

The Sonic Boom

Most modern jet fighters are supersonic aircraft. They are capable of travelling at speeds faster than the speed of sound. During a ceremonial fly past, you must have noticed that as these aircraft fly low overhead, at supersonic speed, they create a sonic boom or a loud bang.

This happens because as the aircraft passes, air parts and moves out of the way. As the air separates and moves out of the path, pressure of the air changes, these changes in pressure create sound waves which travel at the speed of sound. Since the aircraft is travelling at the speed of sound or ever faster, there is a sudden increase in air pressure. High pressure air moves away and when it reaches the ground it can be heard as a loud boom. When jet fighters fly over land, they generally go slower than the speed of sound because these loud booms can be damaging.