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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.
If the distance from the transducer to the reflector is known, and the time taken from the transmit to the receive pulse is known, then the speed of sound in water can be calculated. Transducers used in sound velocity probes are typically of a high frequency (around 1 - 4 MHz) as the transmit and receive distances are close enough to mitigate ...
c is the speed of sound in the medium, which in air varies with the square root of the thermodynamic temperature. By definition, at Mach 1, the local flow velocity u is equal to the speed of sound. At Mach 0.65, u is 65% of the speed of sound (subsonic), and, at Mach 1.35, u is 35% faster than the speed of sound (supersonic).
Sound intensity is defined as the time averaged product of sound pressure and acoustic particle velocity. [8] Both quantities can be directly measured by using a sound intensity p-u probe comprising a microphone and a particle velocity sensor , or estimated indirectly by using a p-p probe that approximates the particle velocity by integrating ...
where is the Laplace operator, is the acoustic pressure (the local deviation from the ambient pressure), and is the speed of sound. A similar looking wave equation but for the vector field particle velocity is given by
Figure 1. Table 1's data in graphical format. Although given as a function of depth [note 1], the speed of sound in the ocean does not depend solely on depth.Rather, for a given depth, the speed of sound depends on the temperature at that depth, the depth itself, and the salinity at that depth, in that order.
The speed of sound (i.e., the longitudinal motion of wavefronts) is related to frequency and wavelength of a wave by =.. This is different from the particle velocity , which refers to the motion of molecules in the medium due to the sound, and relates to the plane wave pressure to the fluid density and sound speed by =.
The speed of sound depends on the medium the waves pass through, and is a fundamental property of the material. The first significant effort towards measurement of the speed of sound was made by Isaac Newton. He believed the speed of sound in a particular substance was equal to the square root of the pressure acting on it divided by its density: