Speed of sound
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The speed of sound is the distance travelled per unit time by a sound wave as it propagates through an elastic medium.
At 20 °C, the speed of sound in air is about 343 meters per second (1,235 km/h) or a kilometer in 2.9 s. It depends strongly on temperature, but also varies by several meters per second, depending on which gases exist in the medium through which a soundwave is propagating.
In common everyday use, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: sound travels most slowly in gases, faster in liquids and even faster in solids. For example, sound travels at 343 m/s in air; it travels at 1,480 m/s in water (4.3 times as fast as in air); and at 5,120 m/s in iron (about 15 times as fast as in air). In an exceptionally stiff material such as diamond, sound travels at 12,000 meters per second, about 35 times as fast as in air, which is around the maximum speed that sound will travel under normal conditions.
