# Voltage level

In communications engineering, voltage level denotes the specification of an electrical voltage in logarithmic form. Since it is related information, the voltage reference value must also be given. In audio engineering , this information is given in the form of the reference level .

## General

The voltage level

${\ displaystyle L_ {U} = 20 \ lg \ left ({\ frac {U} {U_ {0}}} \ right) \, \ mathrm {dB} = 10 \ lg \ left ({\ frac {U ^ {2}} {{U_ {0}} ^ {2}}} \ right) \, \ mathrm {dB}}$

is determined by the voltage under consideration and the reference value . The right-hand form indicates that the approach is defined as the logarithmic ratio of voltage squares and explains why the auxiliary unit of measurement deciBel (dB = 0.1 Bel ) is used. The voltage squared ratio is to be understood as the ratio of electrical power that a fixed electrical resistance absorbs, at which an electrical voltage with the rms value or is applied. ${\ displaystyle U}$ ${\ displaystyle U_ {0}}$${\ displaystyle L_ {U}}$${\ displaystyle U}$${\ displaystyle U_ {0}}$

There are several reasons for the logarithmic level specification:

• The voltage range to be specified often includes several powers of ten . The voltage level can, for. B. Present measured values ​​more clearly in diagrams and characteristics .
• If you connect several modules in series, each one influences the amplitude of the signal in its own way . The amplitude can be increased (gain) or decreased ( damping ).

This behavior is indicated by a gain factor. If it is greater than 1, it is referred to as amplification, if it is smaller than 1, it is referred to as attenuation. In order to be able to calculate more easily which voltage is present at the end of such a chain, the logarithmic unit of the voltage level has been introduced. The logarithmic ratio of the decibel is compared with a reference value (a voltage).

This simplifies the multiplying and dividing otherwise necessary for gain factors to simply adding and subtracting the logarithmic voltage levels.

In addition to the voltage level (with voltage adjustment ), the level specification in the form of power levels is also common for power specifications.

## literature

• Herbert Bernstein: LF and HF measurement technology . Measuring with oscilloscopes, network analyzers and spectrum analyzers, Springer Fachmedien, Wiesbaden 2015, ISBN 978-3-658-07377-0 .
• Michael Dickreiter , Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.): Manual of the recording studio technology . 8th revised and expanded edition, 2 volumes, Verlag Walter de Gruyter, Berlin / Boston 2014, ISBN 978-3-11-028978-7 .
• Rudolf Nocker: Digital Communication Systems. 1. Volume, Basics of Baseband Transmission Technology, Friedrich Vieweg & Sohn Verlag, Wiesbaden 2004, ISBN 978-3-528-03976-9 .
• Stefan Weinzierl (Ed.): Handbook of audio technology . Springer Verlag, Berlin 2008, ISBN 978-3-540-34300-4 .