Field, power, and root-power quantities

A power quantity is a power or a quantity directly proportional to power, e.g., energy density, acoustic intensity, and luminous intensity.[1]

A field quantity is a quantity such as voltage, current, sound pressure, electric field strength, speed, or charge density, the square of which, in linear systems, is proportional to power.[2] The term root-power quantity was introduced in the ISO 80000-1#Annex C, defined as the square root of a power quantity; it replaces and deprecates the term field quantity.

If a field quantity is a complex value (e.g., a phasor), then its magnitude is implied in the logarithm calculations involved. The phrase "root-power quantity" avoids this ambiguity by definition, as power is always positive, and its square root is always real-valued.

The distinctions here described have implications for the definition of decibel, which depends on whether the measured property is a power quantity or a field quantity. So does the level of a root-power quantity or of a power quantity.

See also

References

  1. ↑ Ainslie, M. A. A Century of Sonar: Planetary Oceanography, Underwater Noise Monitoring, and the Terminology of Underwater Sound. Acoustics Today (2015)
  2. ↑ Brian C.J. Moore (1995). Hearing. Academic Press. p. 11. ISBN 9780080533865.
This article is issued from Wikipedia - version of the Wednesday, November 04, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.