Brent Barwick, age 11, of Bethlehem, Pa., for his question:

IS THE SPEED OF SOUND ALWAYS THE SAME?

The speed of sound is not always the same. Two factors determine the speed of sound: the density of the medium  through which the sound waves travel and the elasticity of the medium.

The more elastic a medium, the greater the speed of sound. The denser a medium, the slower the speed of sound.

Steel is 6,000 times denser than air. But it is also two million times more elastic. Therefore, sound travels more swiftly through steel than through air. Sound travels at about 16,400 feet per second in steel but only about 1,087 feet per second in air.

Seed of sound also changes in the air with the temperature. It increases by about one foot each second for each increase of one degree Fahrenheit.