Lee Dryden, age 11, of Columbus, Ohio,
How fast does sound travel?
The speed of sound is not constant. It travels faster on a hot day than on a cold day. It travels faster through water than through air, So there is no one answer to the speed of sound. We have to take into consideration the temperature and the substance through which the sound is traveling.
In air at zero degrees Centigrade, the speed of sound is about 1,087 feet a second. This is more than a mile in five seconds. The conditions give us a basis for a rough standard spend of sound. Engineers keep this rough standard in mind when designing planes, jets and rockets. They call it Mach I and figure it to be plus or minus 600 miles an hour. Some of our experimental rocket planes fly at Mach III, which is plus or minus 1,800 miles an hour.
Sound, then, is a slowpoke when compared with our fastest missiles. It gains a little, however, with increasing temperature. It speeds up about two feet per second with every Centigrade dogroe. Through air at 60 degrees Centigrade the speed of sound is about 1,200 feet a second or about 700 miles an hour.
Through water, which is denser then air, sound travels still faster. Its speed is about 5,000 feet a second, almost five times faster than through air. This is about 3,000 miles an hour, faster than our fastest jets but slower than our missiles.
Planes cannot fly through water or steel. These substances are too dense. With sound, however, conditions are reversed. The denser a substance the faster sound can travel through it. The sound of a hammer blow on a steel girder whizzes along at about 16,500 feet or more than three miles a second. Sound. is caused by vibrating particles. Air, water, steel and all the substances we know are composed of particles.
Sound begins when something strikes or crashes through those particles. The particles at the source are set jostling or vibrating. They jostle their neighbors. The neighboring particles vibrato and in turn jostle each other. The vibrations are carried out from the center in a growing circle.
Sound needs these particles in order to travel. It cannot travel in a vacuum. The more particles, the faster it can travel. This is why the density of a substance affects the speed of sound.
Air is composed of gases. Its particles are free and not packed closely together. A vibrating particle has further to reach to jostle its neighbor. The speed of sound, through sir is therefore slow. Water particles are more closely knit and sound passes along faster. The particles of steel ere locked together and, the vibration of sound can whiz along at the terrific speed of three miles a second.