Why not just use B rather than dB?

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Discussion Overview

The discussion centers around the use of the decibel (dB) unit instead of the bel (B) in measuring sound intensity and other power ratios. Participants explore historical, practical, and perceptual reasons for this choice, touching on concepts from acoustics and logarithmic scales.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that the decibel was originally called the Transmission Unit, and the bel was defined later as a power ratio.
  • One participant explains that using bels would often require decimal fractions for measurements, while decibels allow for integer values in common comparisons.
  • Another participant mentions that sensitivity of perception is a key reason for the decibel's use, suggesting that a 1 dB change is the smallest increment discernible by the most sensitive listeners.
  • Some participants introduce the neper as a more fundamental unit than the bel, discussing its relation to natural logarithms and historical context regarding measurement systems.

Areas of Agreement / Disagreement

Participants express various viewpoints on the reasons for using decibels over bels, with no consensus reached on a single explanation. Multiple competing views regarding historical and perceptual factors remain present in the discussion.

Contextual Notes

Participants reference historical definitions and practical applications of the decibel and bel, but the discussion does not resolve the complexities of these relationships or the implications of using different logarithmic bases.

Who May Find This Useful

Readers interested in acoustics, measurement units, and the historical development of scientific terminology may find this discussion relevant.

xorg
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Hi,

My question is very simple but I have not found on google. Why Decibel unit employs Deci?
I know Deci = 0.1, but why not just use B rather than dB? Is there some historical reason?

Thank you, enjoyed the forum, it is my first post.
 
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The decibel was proposed first, it was originally called the Transmission Unit. The Bel was defined later because it is a straight power ratio.

http://en.wikipedia.org/wiki/Decibel
 
xorg said:
Hi,

My question is very simple but I have not found on google. Why Decibel unit employs Deci?
I know Deci = 0.1, but why not just use B rather than dB? Is there some historical reason?

Thank you, enjoyed the forum, it is my first post.
Hi xorg. http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

A bel is the log to base 10 of a power ratio. In practice, if we used bels we'd frequently be relying on a decimal fraction for common measurement comparisons. By using the much smaller measure, decibel, we lift the common measures into integers.

It's a bit like expressing your height in metres. The all-important part is the fractional bit, but we conventionally tend to pay less heed to that part of a number.
 
Last edited by a moderator:
Sensitivity of perception is the most natural reason
 
zoki85 said:
Sensitivity of perception is the most natural reason
Ah, that reminds me--I've heard it said that a 1decibel step in loudness is about the smallest increment that even the most astute listener can discern. Most of us can perceive a change in sound only if it's at least 2dB. I'm in no position to argue with that figure.
 
Last edited:
The neper is more fundamental than the bel. It is the natural log of a power ratio. http://en.wikipedia.org/wiki/Neper

It is because we use a base 10 number system that we used base 10 logarithms to keep the conversions simple.
Hence in the days of the slide rule, the bel dominated rather than the neper.

Somewhere in my collection is some old German calibration equipment for telephone bearers that is calibrated in nepers.
 

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