A Sound Question

Does sound travel farther over a cool area like a frozen lake or over a warm area such as a desert?

• A. It travels farther over a cool area because the sound is refracted toward or along the ground.
• B. Neither, although sound travels faster in warm air then in cool air, it will travel the same distance in either case.
• C. Over a warm area. Since the sound travel faster, it has less time to be attenuated or absorbed and will travel farther.
• D. I saw Julie Andrews in the Sound Of Music. Does that count?

See if you picked correctly.

Answer

A Sound Question - Answer = A

While sound does travel faster in warm air, it doesn't necessarily travel father. If sound is traveling over a warm area, the temperature normally decreases with increased height, thus the top part of the horizontally traveling sound wave will propagate slower than the lower part. This causes an upward refraction of the sound, bending it away from the ground. However, over a cold area, such as a frozen lake, the upper air may actually be warmer than the lower layer of air. This causes the sound wave to travel faster in the upper region resulting in refraction of the sound towards (along) the ground. And the sound will "travel" farther over the cold surface than over the warm surface. See below. (Some information taken from Flying Circus of Physics by Jearl Walker)

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