bel

bel

a unit for comparing two power levels, equal to the logarithm to the base ten of the ratio of the two powers.

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

bel

[bel]

(physics)

A dimensionless unit expressing the ratio of two powers or intensities, or the ratio of a power to a reference power, such that the number of bels is the common logarithm of this ratio. Symbolized b; B.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

bel

A unit of sound level which denotes the ratio between two quantities proportional to power; the number of bels equals the logarithm of this ratio, to the base 10; 1 bel=10 decibels.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

BEL

bell

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

bell character

The control code used to sound an audible bell or tone in order to alert the user (ASCII 7, EBCDIC 2F).

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deciBel

A unit of measurement of the loudness or strength of a signal. One deciBel is considered the smallest difference in sound level that the human ear can discern. Created in the early days of telephony as a way to measure cable and equipment performance and named after Alexander Graham Bell, deciBels (dBs) are a relative measurement derived from two signal levels: a reference input level and an observed output level. A deciBel is the logarithm of the ratio of the two levels. One Bel is when the output signal is 10x that of the input, and one deciBel is 1/10th of a Bel.

Sound Levels
A whisper is about 20 dB. A normal conversation is typically from 60 to 70 dB, and a noisy factory from 90 to 100 dB. Loud thunder is approximately 110 dB, and 120 dB borders on the threshold of pain. In 1883, the volcano on the Indonesian island of Krakatoa erupted. A hundred miles away, the sound level reached more than 170 dB, deafening everyone who survived. See dBm.

INCREASE IN POWER LEVELS (WATTS)Formula is dB=10*log(P1/P2)DeciBels   Output Signal Strength
       3dB           2x
       6dB           4x
      10dB (1 Bel)  10x
      20dB         100x
      30dB       1,000x
      40db      10,000x


   ATTENUATION OF AMPLITUDE (VOLTS or AMPS)Formula is dB=20*log(A1/A2)DeciBels   Output Signal Strength
      -3dB        0.707x
      -6dB        0.5x
     -10dB        0.316x
     -20dB        0.1x
     -30dB        0.032x
     -40db        0.010x

Bels and Bells

Quite a lot was named after Alexander Graham Bell. Throughout the 20th century, the Bell name was ubiquitous. It will live on with the deciBel.

Copyright © 1981-2025 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Bel

 

the unit for a relative logarithmic quantity (the logarithm of the ratio between two physical quantities of the same name) that is used in electrical engineering, radio engineering, acoustics, and other branches of physics. It is designated by the letter B and is named after the American inventor of the telephone, A. G. Bell. The number of bels N, which corresponds to the ratio of two energy quantities P₁ and P₂ (which relate to power, energy, energy density, and so on), is expressed by the formula N = log (P₁/P₂); for “force” magnitudes F₁ and F₂ (voltage, current strength, pressure, field strength, and others), it is expressed as N = 2 log (F₁/F₂). The tenth part of a bel, called a decibel (dB), is usually used.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.