# Difference between revisions of "Bel"

(hope my adjustments are right) |
|||

Line 1: | Line 1: | ||

− | The '''bel''' is a logarithmical unit used to express relative difference in intensity or power between two signals, usually acoustic. Because of the fact that the Bel unit is too large for everyday use most of the times it is used as the more convenient '''decibel''' (abbreviated to '''dB'''). | + | The '''bel''' ('''B''') is a logarithmical unit used to express relative difference in intensity or power between two signals, usually acoustic. Because of the fact that the Bel unit is too large for everyday use most of the times it is used as the more convenient '''decibel''' (abbreviated to '''dB'''). |

Decibel is equal to ten times the common logarithm of the ratio of the two levels. | Decibel is equal to ten times the common logarithm of the ratio of the two levels. | ||

Line 19: | Line 19: | ||

::<math>{di\! f\!\! f} = 2 \cdot \log_{10}\left(\frac{p_2}{p_1}\right )</math> because <math>\log_{10}(a^2) = 2 \cdot \log_{10}(a)</math> | ::<math>{di\! f\!\! f} = 2 \cdot \log_{10}\left(\frac{p_2}{p_1}\right )</math> because <math>\log_{10}(a^2) = 2 \cdot \log_{10}(a)</math> | ||

− | In this scale, it means an increase of 20 | + | In this scale, it means an increase of 20 B is equal to a ten-fold ratio, or 6 B a two-fold ratio (<math>2 \cdot \log_{10}(2)</math> ''is approximately equal to 6''). |

[[Category:Technical]] | [[Category:Technical]] |

## Revision as of 17:52, 14 June 2007

The **bel** (**B**) is a logarithmical unit used to express relative difference in intensity or power between two signals, usually acoustic. Because of the fact that the Bel unit is too large for everyday use most of the times it is used as the more convenient **decibel** (abbreviated to **dB**).

Decibel is equal to ten times the common logarithm of the ratio of the two levels.

In case of the decibel we have a *10* factor:

There is a second definition of the decibel. In acoustics, it is used to express the ratio in sound pressure, because power is roughly proportional to the square of effective sound pressure.

Let 'p' be pressure, 'P' power.

- because

In this scale, it means an increase of 20 B is equal to a ten-fold ratio, or 6 B a two-fold ratio ( *is approximately equal to 6*).