Implications
It is essential to know which category a measurement belongs to when using decibels (dB) for comparing the levels of such quantities. A change of one bel in the level corresponds to a 10× change in ''power'', so when comparing power quantities ''x'' and ''y'', the difference is defined to be 10×log10(''y''/''x'') decibel. With root-power quantities, however the difference is defined as 20×log10(''y''/''x'') dB. In the analysis of signals and systems using sinusoids, field quantities and root-power quantities may be complex-valued, as in the propagation constant."Root-power quantity" vs. "field quantity"
In justifying the deprecation of the term "field quantity" and instead using "root-power quantity" in the context of levels, ISO 80000 draws attention to the conflicting use of the former term to mean a quantity that depends on the position,ISO 80000-1:2009 § C.2 which in physics is called a '' field''. Such a field is often called a ''field quantity'' in the literature, but is called a ''field'' here for clarity. Several types of field (such as the electromagnetic field) meet the definition of a root-power quantity, whereas others (such as the Poynting vector andSee also
* Level (logarithmic quantity) * Fresnel reflection field and power equations * Sound level, defined for each of several quantities associated with soundReferences
{{reflist Mathematical terminology