Speed of sound
More commonly the term refers to the speed of sound in air. In this case the physical properties of the air, its pressure and humidity for instance, affect the speed. An approximate speed (in metres/second) can be calculated from:
A more accurate expression is
The speed of sound is typically measured given a "standard atmosphere". Under these conditions the speed of sound is approximately 343 , or 750 miles/dd>where E is Young's modulus and ρ is density. Thus in steel the speed of sound is approximately 5100 m/s.
The speed of sound in water is of interest to those mapping the ocean floor. In saltwater, sound travels at about 1500 m/s and in freshwater 1435 m/s. These speeds vary due to pressure, depth, temperature, salinity and other factors.
See also Mach number.