Search results
Results from the WOW.Com Content Network
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.
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).
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. [1]
This may be pictured as the superposition of two waveforms of arbitrary profile, one traveling up the x-axis and the other down the x-axis at the speed . The particular case of a sinusoidal wave traveling in one direction is obtained by choosing either f {\displaystyle f} or g {\displaystyle g} to be a sinusoid, and the other to be zero, giving
In acoustics, Stokes's law of sound attenuation is a formula for the attenuation of sound in a Newtonian fluid, such as water or air, due to the fluid's viscosity.It states that the amplitude of a plane wave decreases exponentially with distance traveled, at a rate α given by = where η is the dynamic viscosity coefficient of the fluid, ω is the sound's angular frequency, ρ is the fluid ...
x is the space variable along the direction of propagation of the sound waves. This equation is valid both for fluids and solids. In fluids, ρc 2 = K (K stands for the bulk modulus); solids, ρc 2 = K + 4/3 G (G stands for the shear modulus) for longitudinal waves and ρc 2 = G for transverse waves. [citation needed]
For a freestream velocity impacting a surface of area , which is inclined at an angle relative to the freestream, the change in normal momentum is and the mass flux incident on the surface is , with being the freestream air density. Then the momentum flux, equal to the force exerted on the surface , from Newton's second law is equal to:
Those physical properties and the speed of sound change with ambient conditions. For example, the speed of sound in gases depends on temperature. In 20 °C (68 °F) air at sea level, the speed of sound is approximately 343 m/s (1,230 km/h; 767 mph) using the formula v [m/s] = 331 + 0.6 T [°C].