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The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. More simply, the speed of sound is how fast vibrations travel. At 20 °C (68 °F), the speed of sound in air is about 343 m/s (1,125 ft/s; 1,235 km/h; 767 mph; 667 kn), or 1 km in 2.91 s or one mile in 4.69 s.
The speed of sound increases with height in two regions of the stratosphere and thermosphere, due to heating effects in these regions. Mach number is a measure of the compressibility characteristics of fluid flow : the fluid (air) behaves under the influence of compressibility in a similar manner at a given Mach number, regardless of other ...
The speed of sound decreases with decreasing temperature, so this also creates a negative sound speed gradient. [48] The sound wave front travels faster near the ground, so the sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. [49]
In acoustics, the sound speed gradient is the rate of change of the speed of sound with distance, for example with depth in the ocean, [1] or height in the Earth's atmosphere. A sound speed gradient leads to refraction of sound wavefronts in the direction of lower sound speed, causing the sound rays to follow a curved path. The radius of ...
Although "subsonic" and "supersonic" usually refer to speeds below and above the local speed of sound respectively, aerodynamicists often use these terms to refer to particular ranges of Mach values. When an aircraft approaches transonic speeds (around Mach 1), it enters a special regime.
The speed of sound in any chemical element in the fluid phase has one temperature-dependent value. In the solid phase, different types of sound wave may be propagated, each with its own speed: among these types of wave are longitudinal (as in fluids), transversal, and (along a surface or plate) extensional.
For many applications of sonar the speed of sound can be assumed to be an average speed of 1500 meters per second. However, the speed of sound in seawater can vary from 1440 to 1570 meters per second. [1] An example of a sound velocity probe – the Teledyne Odom Digibar Pro
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level , this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h).