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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 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.
From the speed of sound, the temperature of the air in the planetary boundary layer can be computed. [2] The maximum altitude range of RASS systems is typically 750 metres (2,460 ft), although observations have been reported up to 1.2 km (3,900 ft) in moist air.
Now, the combination of both isotropy and Galilean covariance tells us that the permissible velocities of the sound waves at a given point x, has to satisfy (()) = () This restriction can also arise if we imagine that sound is like "light" moving through a spacetime described by an effective metric tensor called the acoustic metric .
As altitude increases through the atmosphere, the first sound waves to disappear are the high pitched, high-frequency (short wavelength) ones. At a certain altitude (roughly 160 kilometers (99 mi)) even the lowest frequency tone that can be heard by a human being (around 20 Hz) no longer can be transmitted.
However, a cylinder closed at both ends can also be used to create or visualize sound waves, as in a Rubens Tube. The resonance properties of a cylinder may be understood by considering the behavior of a sound wave in air. Sound travels as a longitudinal compression wave, causing air molecules to move back and forth along the direction of travel.
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.
An acoustic wave is a mechanical wave that transmits energy through the movements of atoms and molecules. Acoustic waves transmit through fluids in a longitudinal manner (movement of particles are parallel to the direction of propagation of the wave); in contrast to electromagnetic waves that transmit in transverse manner (movement of particles at a right angle to the direction of propagation ...