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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 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.
If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations. In fresh water the speed of sound is approximately 1,482 m/s (5,335 km/h; 3,315 mph). In steel, the speed of sound is about 5,960 m/s (21,460 km/h; 13,330 mph).
Most sound radiation is caused by bending (or flexural) waves, that deform the structure transversely as they propagate. Bending waves are more complicated than compressional or shear waves and depend on material properties as well as geometric properties. They are also dispersive since different frequencies travel at different speeds.
where n is a positive integer (1, 2, 3...) representing the resonance node, L is the length of the tube and v is the speed of sound in air (which is approximately 343 metres per second [770 mph] at 20 °C [68 °F]).
A rugged ultrasonic thickness gauge determines sample thickness by measuring the amount of time it takes for sound to traverse from the transducer through the material to the back end of a part and back. The ultrasonic thickness gauge then calculates the data based on the speed of the sound through the tested sample.
Kundt's tube is an experimental acoustical apparatus invented in 1866 by German physicist August Kundt [1] [2] for the measurement of the speed of sound in a gas or a solid rod. The experiment is still taught today due to its ability to demonstrate longitudinal waves in a gas (which can often be difficult to visualise).
Experimental image of surface acoustic waves on a crystal of tellurium oxide [1]. A surface acoustic wave (SAW) is an acoustic wave traveling along the surface of a material exhibiting elasticity, with an amplitude that typically decays exponentially with depth into the material, such that they are confined to a depth of about one wavelength.