Talk:Decibel

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dB as a "unit" of power/field quantities[edit]

Everywhere in this article, "unit" is to be understood as a logarithmic unit, not as in units of measurement. Since the former redirects to logarithmic scale -- article which does not even mention the word "unit" --, this shorthand is misleading in the present article. For example, decibel can be said to be a unit of power level, but it cannot be said to be a unit of power (perhaps saying it's a power scale is okay). In other words, decibels are rightly a unit of level-type derived quantities; but when referring to the primary power- or field-type quantities, decibel cannot be said to be directly a unit of the primary quantities themselves, only as a unit of the logarithmic ratio of such primary quantities. Therefore, I'd like to propose rephrasing "unit" as "level unit" or "scale" where appropriate. Fgnievinski (talk) 02:39, 15 May 2015 (UTC)

The best way of solving this problem is to state clearly, and early on in the lede, that the decibel is unit of level. Further down, by way of clarification, one could then explain the implications of this, including the fact that it is not a unit of power. Using the term "level unit" is OK to reinforce this (though not really needed all the way through IMHO), because that is literally what it is, but "scale" would not be correct. Dondervogel 2 (talk) 08:16, 15 May 2015 (UTC)
Are you saying that "scale" would be an incorrect shorthand for "logarithmic scale"? I assume you don't dispute the latter aptly describes the decibel, analogous to decade. Fgnievinski (talk) 03:24, 16 May 2015 (UTC)
I'm saying that a decibel is a unit of level, and a level is a logarithmic quantity. It is therefore correct to say that a decibel is a unit of a logarithmic quantity. A logarithmic scale is something else, implying some range of values in which logarithmic quantities are expressed (e.g., the scale of notes on a piano). So 'decibel' and 'logarithmic scale' are not synonyms. Dondervogel 2 (talk) 08:36, 16 May 2015 (UTC)
I am against the use of the word "unit". Unit means "one". When you have zero kg, zero meter or zero ampere, you have nothing, niet, nada. However, when you have 0 dB, you have a 1:1 ratio of power/voltage/current. Personnaly, i'd suggest "Logarithmic expression". Normand Martel 09:43, 02 December 2015 (UTC)
The decibel is a unit in log space. In the logarithmic world, a 1:1 ratio is precisely what you say: zilch = niets = niente = nada. Dondervogel 2 (talk) 14:01, 2 December 2015 (UTC)

Does "dB re" mean "decibels relative to" or "decibels with reference to"?[edit]

Does anyone know of a source that gives a definitive answer to the meaning of "re" in "dB re"? Dondervogel 2 (talk) 23:43, 13 November 2015 (UTC)

this is a common abbreviation of "with reference to" for example "dB re 20 µPa" for sound pressure level. It is not standardized by my knowledge. — Preceding unsigned comment added by Mvenl (talkcontribs) 19:57, 9 December 2015 (UTC)
@Mvenl Thank you for this explanation. Can you cite a source to back up "with reference to"? Dondervogel 2 (talk) 00:36, 10 December 2015 (UTC)

Unintended mistake when interpreting 80000-3[edit]

Please comment and contribute:

Almost all formulas for calculations with levels that are expressed in decibel presume that the decibel has no dimension, and certainly not has a value. This is valid for most, if not all(!) formulas in ISO standards regarding acoustics, but also for formulas is many legal regulations and (educational) publications related to noise assessment.

If these formulas are applied with the notion that, according to ISO80000-3, a dB equals 0,115..., then huge mistakes will be made. This is a serious issue that has to be solved. As long as it is not solved this wiki-article should contain some kind of text addressing that. I like to prepare such a text but want to know what is concidered an appropriate location and heading.

Michiel van Eeden — Preceding unsigned comment added by Mvenl (talkcontribs) 15:29, 5 December 2015 (UTC)

logarithmic mean[edit]

I'm sure I'm misunderstanding something, but could someone just check to see that using the equation in the logarithmic mean article actually gives you an answer of 87? I can get 87 by converting 90 and 70 dB out of dB, using the arithmetic mean and then converting back to dB. But using the equation in logarithmic mean, I get Mlm(90,70) = (90-70)/(ln(90)-ln(70)) = 79.5816. Additionally, in the Inequalities section, it says that the logarithmic mean is smaller than the arithmetic mean. How can this be the right equation if the result is supposed to be 87? If it's not the correct equation, there should be some clarification before direction to the logarithmic mean article. -Wongba (talk) 13:26, 8 January 2016 (UTC)

Accoustic math error?[edit]

There seems to be an error in the math in section 5.1 (Uses/Accoustics) "the base-10 logarithm of 10^12 is 12, which is expressed as a sound pressure level of 120 dB re 20 micropascals." Earlier in the same section it states the formula for amplitude ratios as dBspl = 20 Log (Prms/Pref), which would make 120 dBspl equal to a ratio of 10^6 not 10^12. I'm not an expert but this seemed like a error to me. I didn't edit it on the page because I don't feel like I know enough to definitively correct this incongruity.

Also, the reference to the "Trillion" ratio stated in section 5.1 "The ratio of the sound intensity that causes permanent damage during short exposure to the quietest sound that the ear can hear is greater than or equal to 1 trillion (10^12).[33]" actually states the level as 120 dB not "equal to or greater than 1 trillion". This induction based on aparent faulty math should probably be corrected as well. 131.137.245.208 (talk) 13:09, 4 February 2016 (UTC)Malcolm

Ratio of 10^6 in pressure, ratio of 10^12 in intensity. - David Biddulph (talk) 13:30, 4 February 2016 (UTC)