Wave amplitude formula_4 described by the equation: where The units of the amplitude depend on the type of wave. Transverse mechanical waves (e.g., a wave on a string) have an amplitude expressed as a distance (e.g., meters), longitudinal mechanical waves (e.g., sound waves) use units of pressure (e.g., pascals), and electromagnetic waves (a form of transverse vacuum wave) express the amplitude in terms of its electric field (e.g., volts/meter). The wavelength formula_30 is the distance between two sequential crests or troughs (or other equivalent points), generally is measured in meters. A wavenumber formula_17, the spatial frequency of the wave in radians
Sound power temperature, the sound power level at distance "r" from the sound source is approximately related to sound pressure level (SPL) by where Derivation of this equation: For a "progressive" spherical wave, where "z" is the characteristic specific acoustic impedance. Consequently, and since by definition , where is the reference sound pressure, The sound power estimated practically does not depend on distance. The sound pressure used in the calculation may be affected by distance due to viscous effects in the propagation of sound unless this is accounted for. Sound power Sound power or acoustic power is the rate at which sound