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Decibel - History of bels and decibels

Decibel - History of bels and decibels: Encyclopedia II - Decibel - History of bels and decibels

A bel (symbol B) is a unit of measure of ratios, such as power levels and voltage levels. It is mostly used in telecommunication, electronics, and acoustics. Invented by engineers of the Bell Telephone Laboratory to quantify the reduction in audio level over a 1 mile length of standard telephone cable, it was originally called the transmission unit or TU, but was renamed in 1923 or 1924 in honor of the laboratory's found ...

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Decibel, Decibel - 6 dB per bit, Decibel - Absolute measurements, Decibel - Acoustics, Decibel - Definition, Decibel - Electronics, Decibel - History of bels and decibels, Decibel - Merits, Decibel - Optics, Decibel - Reckoning, Decibel - Reference, Decibel - Relative measurements, Decibel - Round numbers, Decibel - Seismology, Decibel - Standards, Decibel - Telecommunications, Decibel - The 4 → 6 energy rule, Decibel - The 789 rule, Decibel - Typical abbreviations, Decibel - Uses, Decibel - dB cheat sheet, Decibel - −3 dB ≈ ½ power, Equal-loudness contour, ITU-R 468 noise weighting, Noise (environmental), Signal noise, Sound pressure level, Weighting filter—discussion of dBA, Decibel magazine

Decibel: Encyclopedia II - Decibel - History of bels and decibels

Decibel - History of bels and decibels

A bel (symbol B) is a unit of measure of ratios, such as power levels and voltage levels. It is mostly used in telecommunication, electronics, and acoustics. Invented by engineers of the Bell Telephone Laboratory to quantify the reduction in audio level over a 1 mile length of standard telephone cable, it was originally called the transmission unit or TU, but was renamed in 1923 or 1924 in honor of the laboratory's founder and telecommunications pioneer Alexander Graham Bell.

The bel was too large for everyday use, so the decibel (dB), equal to 0.1 bel (B), became more commonly used. The bel is still used to represent noise power levels in hard drive specifications.

The neper is a similar unit which uses the natural logarithm. The Richter scale uses numbers expressed in bels as well, though this is implied by definition rather than explicitly stated. In spectrometry and optics, the absorbance unit used to measure optical density is equivalent to −1 B. In astronomy, the apparent magnitude measures the brightness of stars logarithmically, since just as the ear responds logarithmically to acoustic power, the eye responds logarithmically to brightness.

Other related archives

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Adapted from the Wikipedia article "History of bels and decibels", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki

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