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I think some words are necessary about the assumption of non-negative and non-complex input. Unless one disputes decibels being real-valued? For power quantities this follows from the definition of power. But for root-power quantities, the
modulus operation must be involved, either inside the decibel formula or outside, in the presumed input preparation. Otherwise, the equivalence between power and root-power decibel formulations doesn't hold mathematically: 10*log10(F^2)=20*log10(|F|)<>20*log10(F). I suspect this was part of the motivation for ISO 80000 introducing the "root-power" terminology, F=sqrt(√(FF^*)), i.e., by implying that a square root must be invoked after taking the squared norm
absolute square.
fgnievinski (
talk)
02:30, 17 May 2020 (UTC)
ISO 80000-3:2006 used to define the decibel. However, this standard has been superseded by ISO 80000-3:2019, which does not define the decibel. In other words the ISO definition of the dB is no more. I added an explanation to this effect, but this leaves a bit of a vacuum that deserves filling. I'm sure there are lots of alternative definitions out there, but probably none with the consensus and authority implied by ISO 80000. Thoughts? Dondervogel 2 ( talk) 05:48, 16 July 2020 (UTC)
I still say this is uninterpretable. I don't disagree that "Since the human ear is not equally sensitive to all sound frequencies, noise levels at maximum human sensitivity, somewhere between 2 and 4 kHz, are factored more heavily into some measurements using frequency weighting such as Psophometric weighting", aside from the abuse of the term "levels" therein. Yet this pretends to have something to do with decibels. And the added source seems broken. And while I'm a fan of Stevens's power law, I can't see how the see-also there makes any sense. What exactly is the intent of this paragraph? Can we turn it into something sensible, or shall I just delete it again as uninterpretable? Dicklyon ( talk) 04:10, 21 August 2020 (UTC)
Previous discussion indicated that a sorted table might work well in Decibel § Suffixes and reference values. Here's a prototype. There are issues with this implementation so I'm not sure it is worth pursuing further. I do think we should continue to discuss ways to improve presentation of this list. ~ Kvng ( talk) 15:03, 31 October 2020 (UTC)
Category | Unit | Reference | Notes |
---|---|---|---|
Voltage | dBV | voltage relative to 1 volt, regardless of impedance. [1] | This is used to measure microphone sensitivity, and also to specify the consumer line-level of −10 dBV, in order to reduce manufacturing costs relative to equipment using a +4 dBu line-level signal. [2] |
dB(V RMS) | |||
dBu | RMS voltage relative to (i.e. the voltage that would dissipate 1 mW into a 600 Ω load). An RMS voltage of 1 V therefore corresponds to [1] | Originally dBv, it was changed to dBu to avoid confusion with dBV. [3] The "v" comes from "volt", while "u" comes from the volume unit used in the VU meter. [4]dBu can be used as a measure of voltage, regardless of impedance, but is derived from a 600 Ω load dissipating 0 dBm (1 mW). The reference voltage comes from the computation . In professional audio, equipment may be calibrated to indicate a "0" on the VU meters some finite time after a signal has been applied at an amplitude of +4 dBu. Consumer equipment typically uses a lower "nominal" signal level of −10 dBV. [5] Therefore, many devices offer dual voltage operation (with different gain or "trim" settings) for interoperability reasons. A switch or adjustment that covers at least the range between +4 dBu and −10 dBV is common in professional equipment. | |
dBv | |||
dBm0s | voltage relative to 1 millivolt across 75 Ω. [6] | Defined by Recommendation ITU-R V.574. Widely used in cable television networks, where the nominal strength of a single TV signal at the receiver terminals is about 0 dBmV. Cable TV uses 75 Ω coaxial cable, so 0 dBmV corresponds to −78.75 dBW (−48.75 dBm) or approximately 13 nW. | |
dBmV | |||
dBm0s | |||
dBμV | voltage relative to 1 microvolt. 60 dBμV = 0 dBmV. | Widely used in television and aerial amplifier specifications. | |
dBuV | |||
dB(μV RMS) |
References
AFAIR, the lead section used to be relatively reader-friendly. Now it seems to have substantially deteriorated, not to mention the HORRIBLE layout whereby a large technical lookup table, that we don't anyway need to see at this point, forces the lead text into a tiny column. Not good. 2A00:23C8:7B08:6A00:6450:3519:2A88:94C2 ( talk) 23:39, 6 November 2020 (UTC)
@ Dicklyon: ... are related in a simple way for harmonic signals, but not in general. For this reason the wording "(usually equivalently)" is incorrect. Dondervogel 2 ( talk) 07:31, 12 November 2020 (UTC)
As much as I love all the technical stuff in this article, probably 90% of the people who find this are just looking for information about "how loud is x vs y" sound pressure levels, which are often reported for point sources in "dB" without any distance or reference level specified.
It might be good to have a simple explainer in the introduction that the "dB" people have heard of is only one of many types, that it's short for "dBSPL", and that the measurements they've heard of are largely meaningless because they don't include distance. — Omegatron ( talk) 22:37, 3 December 2020 (UTC)
@ Kvng:@ Dondervogel 2: I am afraid this is a misinterpretation. As a unit, there is one decibel only, equal to the ratio 101/10:1 for a power quantity and 101/20:1 for a root-power quantity. All the attachments belong to the quantity name, not to the quantity unit name, see ISO standards: "Any attachment to a unit symbol as a means of giving information about the special nature of the quantity or context of measurement under consideration is not permitted." [1]. Particularly for dB, see [2]. JOb ( talk) 10:52, 24 December 2020 (UTC)
References
I think the lead may be too technical or confusing for some people. I have a very rough idea of these topics but let's look at it from a layperson's perspective, to which I'm closer than to that of a knowledgeable person. It says:
I feel very strongly that many people will be totally confused by this little paragraph. If they wanna know things such as "what's the loudness difference from one decibel to another?" (I know perceived loudness is measured differently, but bear with me, since again, we're looking at it from a layperson's perspective). Unlike centimeters or inches, which many people can visualize, I don't think the bel is a familiar unit of measurement. I know experts will cringe at the suggestion, but maybe we could add some plainer explanation, with some visual analogies, somewhere in the lead? I would attempt to do it myself, but I don't know much about the topic beyond what one picks up producing and compressing music at home for fun. By the way, if you look up "power ratio" on Google the first result is from Investopedia (finance-related website) and the next seem to be references for engineers or physicists. -- Paper wobbling sound ( talk) 06:15, 13 March 2021 (UTC)
You are right (I agree to your position). Bel or db is not a "class" of it´s own. First "comes" a Ratio (r)of Power P, for example r = P2/P1. In many cases it may be of advantage, to say: x = log P2/P1 where x is said to be x Bel or xB. Where is the trouble for nontechnicians? Here it is: Bel oder decibel (dB) is not a unit! You should not recognize xB as a mathematical product like x multiplied by B. B is not a factor like all (!) other Units. It`s an How To Do, nothing else. Edgar Wollenweber (Germany) -- 79.204.169.180 ( talk) 17:42, 16 April 2021 (UTC)
I believe that Wikipedia should feature a conversion table of units that express ratio. This is not only decibel, but also neper, decade, music intervals from semitone to octave and cents as well... Shall I make a new page and cross-link? -- FDominec ( talk) 08:40, 8 June 2021 (UTC)
The part about uses in acoustics is confusing. First it talks about pressures, for which a factor 20 must be used. Then it apparently mixes between pressures and intensities, and it's not clear what happens with the formulae (see italic):
"The human ear has a large dynamic range in sound reception. The ratio of the sound intensity that causes permanent damage during short exposure to that of the quietest sound that the ear can hear is equal to or greater than 1 trillion (1012).[39] Such large measurement ranges are conveniently expressed in logarithmic scale: the base-10 logarithm of 10^12 is 12, which is expressed as a sound pressure level of 120 dB re 20 μPa. "
However, 20 x log (10^12) = 20 x 12 = 240 ... I've corrected using only intensities for now, but I'm not sure how correct this is. Am I missing something? Can it be explained better and correctly? Kruiser ( talk) 15:24, 14 December 2020 (UTC)
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
Participate in the deletion discussion at the nomination page. — Community Tech bot ( talk) 22:39, 7 January 2022 (UTC)
There is a complication with Fourier transform that it works in linear space, but sometimes people want a spectrum in logarithmic space. As well as I know it, there is no easy trick to doing it, like there is with FFT. That is, no fast logarithmic transform. I don't know what means anything should go here, though, but it might be interesting to mention spectra with a logarithmic frequency axis. Gah4 ( talk) 01:03, 10 February 2022 (UTC)
This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 5 | Archive 6 | Archive 7 | Archive 8 |
I think some words are necessary about the assumption of non-negative and non-complex input. Unless one disputes decibels being real-valued? For power quantities this follows from the definition of power. But for root-power quantities, the
modulus operation must be involved, either inside the decibel formula or outside, in the presumed input preparation. Otherwise, the equivalence between power and root-power decibel formulations doesn't hold mathematically: 10*log10(F^2)=20*log10(|F|)<>20*log10(F). I suspect this was part of the motivation for ISO 80000 introducing the "root-power" terminology, F=sqrt(√(FF^*)), i.e., by implying that a square root must be invoked after taking the squared norm
absolute square.
fgnievinski (
talk)
02:30, 17 May 2020 (UTC)
ISO 80000-3:2006 used to define the decibel. However, this standard has been superseded by ISO 80000-3:2019, which does not define the decibel. In other words the ISO definition of the dB is no more. I added an explanation to this effect, but this leaves a bit of a vacuum that deserves filling. I'm sure there are lots of alternative definitions out there, but probably none with the consensus and authority implied by ISO 80000. Thoughts? Dondervogel 2 ( talk) 05:48, 16 July 2020 (UTC)
I still say this is uninterpretable. I don't disagree that "Since the human ear is not equally sensitive to all sound frequencies, noise levels at maximum human sensitivity, somewhere between 2 and 4 kHz, are factored more heavily into some measurements using frequency weighting such as Psophometric weighting", aside from the abuse of the term "levels" therein. Yet this pretends to have something to do with decibels. And the added source seems broken. And while I'm a fan of Stevens's power law, I can't see how the see-also there makes any sense. What exactly is the intent of this paragraph? Can we turn it into something sensible, or shall I just delete it again as uninterpretable? Dicklyon ( talk) 04:10, 21 August 2020 (UTC)
Previous discussion indicated that a sorted table might work well in Decibel § Suffixes and reference values. Here's a prototype. There are issues with this implementation so I'm not sure it is worth pursuing further. I do think we should continue to discuss ways to improve presentation of this list. ~ Kvng ( talk) 15:03, 31 October 2020 (UTC)
Category | Unit | Reference | Notes |
---|---|---|---|
Voltage | dBV | voltage relative to 1 volt, regardless of impedance. [1] | This is used to measure microphone sensitivity, and also to specify the consumer line-level of −10 dBV, in order to reduce manufacturing costs relative to equipment using a +4 dBu line-level signal. [2] |
dB(V RMS) | |||
dBu | RMS voltage relative to (i.e. the voltage that would dissipate 1 mW into a 600 Ω load). An RMS voltage of 1 V therefore corresponds to [1] | Originally dBv, it was changed to dBu to avoid confusion with dBV. [3] The "v" comes from "volt", while "u" comes from the volume unit used in the VU meter. [4]dBu can be used as a measure of voltage, regardless of impedance, but is derived from a 600 Ω load dissipating 0 dBm (1 mW). The reference voltage comes from the computation . In professional audio, equipment may be calibrated to indicate a "0" on the VU meters some finite time after a signal has been applied at an amplitude of +4 dBu. Consumer equipment typically uses a lower "nominal" signal level of −10 dBV. [5] Therefore, many devices offer dual voltage operation (with different gain or "trim" settings) for interoperability reasons. A switch or adjustment that covers at least the range between +4 dBu and −10 dBV is common in professional equipment. | |
dBv | |||
dBm0s | voltage relative to 1 millivolt across 75 Ω. [6] | Defined by Recommendation ITU-R V.574. Widely used in cable television networks, where the nominal strength of a single TV signal at the receiver terminals is about 0 dBmV. Cable TV uses 75 Ω coaxial cable, so 0 dBmV corresponds to −78.75 dBW (−48.75 dBm) or approximately 13 nW. | |
dBmV | |||
dBm0s | |||
dBμV | voltage relative to 1 microvolt. 60 dBμV = 0 dBmV. | Widely used in television and aerial amplifier specifications. | |
dBuV | |||
dB(μV RMS) |
References
AFAIR, the lead section used to be relatively reader-friendly. Now it seems to have substantially deteriorated, not to mention the HORRIBLE layout whereby a large technical lookup table, that we don't anyway need to see at this point, forces the lead text into a tiny column. Not good. 2A00:23C8:7B08:6A00:6450:3519:2A88:94C2 ( talk) 23:39, 6 November 2020 (UTC)
@ Dicklyon: ... are related in a simple way for harmonic signals, but not in general. For this reason the wording "(usually equivalently)" is incorrect. Dondervogel 2 ( talk) 07:31, 12 November 2020 (UTC)
As much as I love all the technical stuff in this article, probably 90% of the people who find this are just looking for information about "how loud is x vs y" sound pressure levels, which are often reported for point sources in "dB" without any distance or reference level specified.
It might be good to have a simple explainer in the introduction that the "dB" people have heard of is only one of many types, that it's short for "dBSPL", and that the measurements they've heard of are largely meaningless because they don't include distance. — Omegatron ( talk) 22:37, 3 December 2020 (UTC)
@ Kvng:@ Dondervogel 2: I am afraid this is a misinterpretation. As a unit, there is one decibel only, equal to the ratio 101/10:1 for a power quantity and 101/20:1 for a root-power quantity. All the attachments belong to the quantity name, not to the quantity unit name, see ISO standards: "Any attachment to a unit symbol as a means of giving information about the special nature of the quantity or context of measurement under consideration is not permitted." [1]. Particularly for dB, see [2]. JOb ( talk) 10:52, 24 December 2020 (UTC)
References
I think the lead may be too technical or confusing for some people. I have a very rough idea of these topics but let's look at it from a layperson's perspective, to which I'm closer than to that of a knowledgeable person. It says:
I feel very strongly that many people will be totally confused by this little paragraph. If they wanna know things such as "what's the loudness difference from one decibel to another?" (I know perceived loudness is measured differently, but bear with me, since again, we're looking at it from a layperson's perspective). Unlike centimeters or inches, which many people can visualize, I don't think the bel is a familiar unit of measurement. I know experts will cringe at the suggestion, but maybe we could add some plainer explanation, with some visual analogies, somewhere in the lead? I would attempt to do it myself, but I don't know much about the topic beyond what one picks up producing and compressing music at home for fun. By the way, if you look up "power ratio" on Google the first result is from Investopedia (finance-related website) and the next seem to be references for engineers or physicists. -- Paper wobbling sound ( talk) 06:15, 13 March 2021 (UTC)
You are right (I agree to your position). Bel or db is not a "class" of it´s own. First "comes" a Ratio (r)of Power P, for example r = P2/P1. In many cases it may be of advantage, to say: x = log P2/P1 where x is said to be x Bel or xB. Where is the trouble for nontechnicians? Here it is: Bel oder decibel (dB) is not a unit! You should not recognize xB as a mathematical product like x multiplied by B. B is not a factor like all (!) other Units. It`s an How To Do, nothing else. Edgar Wollenweber (Germany) -- 79.204.169.180 ( talk) 17:42, 16 April 2021 (UTC)
I believe that Wikipedia should feature a conversion table of units that express ratio. This is not only decibel, but also neper, decade, music intervals from semitone to octave and cents as well... Shall I make a new page and cross-link? -- FDominec ( talk) 08:40, 8 June 2021 (UTC)
The part about uses in acoustics is confusing. First it talks about pressures, for which a factor 20 must be used. Then it apparently mixes between pressures and intensities, and it's not clear what happens with the formulae (see italic):
"The human ear has a large dynamic range in sound reception. The ratio of the sound intensity that causes permanent damage during short exposure to that of the quietest sound that the ear can hear is equal to or greater than 1 trillion (1012).[39] Such large measurement ranges are conveniently expressed in logarithmic scale: the base-10 logarithm of 10^12 is 12, which is expressed as a sound pressure level of 120 dB re 20 μPa. "
However, 20 x log (10^12) = 20 x 12 = 240 ... I've corrected using only intensities for now, but I'm not sure how correct this is. Am I missing something? Can it be explained better and correctly? Kruiser ( talk) 15:24, 14 December 2020 (UTC)
The following Wikimedia Commons file used on this page or its Wikidata item has been nominated for deletion:
Participate in the deletion discussion at the nomination page. — Community Tech bot ( talk) 22:39, 7 January 2022 (UTC)
There is a complication with Fourier transform that it works in linear space, but sometimes people want a spectrum in logarithmic space. As well as I know it, there is no easy trick to doing it, like there is with FFT. That is, no fast logarithmic transform. I don't know what means anything should go here, though, but it might be interesting to mention spectra with a logarithmic frequency axis. Gah4 ( talk) 01:03, 10 February 2022 (UTC)