What is the speed of sound (20 degrees Celsius in dry air)?

The speed of sound is the distance traveled per unit time by a sound wave propagating through an elastic medium. In dry air at 20 °C, the speed of sound is 343.2 meters per second (1,126 ft/s). This is 1,236 kilometer per hour (768 mph; 667 kn), or a kilometer in 2.914 s or a mile in 4.689 s.

In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance. Sound travels faster in liquids and non-porous solids than it does in air. It travels about 4.3 times as fast in water (1,484 m/s), and nearly 15 times as fast in iron (5,120 m/s), as in air at 20 °C. Sound waves in solids are composed of compression waves (just as in gases and liquids), but there is also a different type of sound wave called a shear wave, which occurs only in solids. These different types of waves in solids usually travel at different speeds, as exhibited in seismology. The speed of a compression sound wave in solids is determined by the medium's compressibility, shear modulus and density. The speed of shear waves is determined only by the solid material's shear modulus and density.

More Info: www.wikipedia.org

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64 Comments

Bill Coe

It is great that you recognized the variance with temperature and moisture content. Why did you not at the same time recognize altitude variation. The decrease of the speed of sound with height is referred to as a negative sound speed gradient.So your answer of 767/768 is correct for 20 degrees, in dry air AT SEA LEVEL.

fdeisner

I remember from school that the speed of sound was 660 miles per hour at sea level. I chose 768 miles per hour as it was the closest to that. Why would you not give the temperature in degrees Fahrenheit as you were looking for miles per hour. I would use degrees celsius if I was looking for kilometers per hour. Just an observation that you should be consistent with metric or non metric measurements.

Sybilla

This question included several multiplications before arriving to kilometres. The only figure I knew was 343.37 metres per second.

Elizabeth Buehler-Miller

I understood the conversion needed, but it was extremely difficult. This should be a question for a higher level.

Julia Brandenburg

The picture of the SST was a great hint as to the correct answer. Once i saw the plane, i knew the answer.

Yvonne C. Wood

Wahoo taking Science all those high school year paid off

littledick

Correct, no guess.

Vaughan Smith

When close to half of participants get a question wrong, I take this as an indicator of a "good" question, one from whose answer a lot of people can learn something

dsneed

Reeeaaallyyy fast.

PhoenixABlaze

Sonic Boom?

innflyte

Re MACH:-In fluid dynamics, the Mach number (M or Ma) (/mɑːk/; German: [max]) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound. M=u/c, where: M is the Mach number, u is the local flow velocity with respect to the boundaries (either internal, such as an object immersed in the flow, or external, like a channel), and c is the speed of sound in the medium.