Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 35. Chapters: 52-Hertz whale, Acoustic attenuation, Acoustic holography, Acoustic impedance, Audio frequency, Audio noise measurement, Audio power, Ceiling level, Crosstalk measurement, Impact insulation class, Loudspeaker measurement, Particle displacement, Particle velocity, Particle velocity probe, Phonomotor, Sabin (unit), Sound, Sound energy, Sound energy density, Sound energy flux, Sound intensity, Sound level meter, Sound power, Sound pressure, Speech interference level, Speed of sound. Excerpt: The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at, the speed of sound is 343.2 metre per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one mile in five seconds. In fluid dynamics, the speed of sound in a fluid medium (gas or liquid) is used as a relative measure of speed itself. The speed of an object (in distance per time) divided by the speed of sound in the fluid is called the Mach number. Objects moving at speeds greater than are traveling at supersonic speeds. The speed of sound in an ideal gas is independent of frequency, but it weakly depends on frequency for all real physical situations. It is a function of the square root of the absolute temperature, but is independent of pressure or density for a given ideal gas. Sound speed is slightly dependent on pressure only because air is not quite an ideal gas. In addition, for different gases, the speed of sound is inversely dependent on square root of the mean molecular weight of the gas, and affected to a lesser extent by the number of ways in which the molecules of the gas can store heat from compression, since sound in gases is a type of compression. Although (in the case of gases only) the speed of sound is...