Neper

The Napier ( unit symbol Np ) is an after Scotsman John Napier ( 1550-1617, Latinized: Napier ) named auxiliary unit for the identification of levels and dimensions ( importance of both terms: Logarithmic see the article size), among others, in electrical engineering and acoustics.

The Napier serves to identify the natural logarithm (ln ) of the ratio of two field sizes, and (instead of field size new name as per DIN 5493:2013-10 " power root size " ):

The following applies:

The Napier is the BIPM for use with the International System of Units (SI) and considered by the International Telecommunication Union as coherent with the SI unit. Together with the above definition of " the Napier is the coherent unit that can be replaced by one, unit number 1, ".

An indication in Napier can be due to the relationship

With the natural logarithm of the ratio can also be complex field quantities elegant treat and so, for example, a complex attenuation factor in damping ratio ( in Napier ) and phase angle separating (in radians ):

Such an account is not possible with the decibel record with no factors. Since the Neper is dimensionless and has the value 1 (as well as the Radiant ), you can simply leave it in calculations. In practice, the Napier is among other things used for historical reasons rather than ratios of field sizes for ratios of energy quantities.

When applied to energy quantities which are proportional to the square of the field variables, the following applies: