Talk:Fluctuation spectrum

Context and Technical tags
I've added these because as of August 2021,
 * it's unclear what area(s) of study the concept belongs to.
 * it's unclear what the concept is used for within those areas.
 * knowledge of all technical terms is assumed.

Maybe these could be partially addressed by this kind of structure: Musiconeologist (talk) 23:05, 28 August 2021 (UTC)
 * Lead section setting the context. For example: "A fluctuation spectrum is a concept used in areas such as . . . These all have the characteristic that . . . A fluctuation spectrum is . . . It is typically used to . . . "
 * More specific definition of what it is. (At present, there isn't any definition.)
 * One or two specific examples from the areas mentioned, in enough detail to show at least qualitatively what a fluctuation spectrum in that field actually is.

Definition
At present the article doesn't define what a fluctuation spectrum is, and the opening sentence confusingly suggests that it is a collection of physical phenomena. I think what it's trying to say is that various phenomena can be characterised as having a fluctuation spectrum.

From instances I've found online, it looks to me as though the actual situation is this:


 * Certain phenomena can be usefully characterised by some variable which fluctuates about a mean or equilibrium value.
 * The fluctuation may be with respect to either time or position.
 * The fluctuation spectrum is simply the frequency spectrum of the fluctuation.
 * For a fluctuation in time, frequency has the usual meaning of cycles per unit time, normally measured in Hz.
 * For a fluctuation with respect to position, frequency refers to spatial frequency, i.e. cycles per unit distance.
 * In either case, the fluctuation spectrum is calculated by taking the Fourier transform of the original data. (So it's transformed either from being a function of time to one of frequency, or from a function of distance to one of spatial frequency.)

If someone can confirm that this is accurate, I'll happily use it to write a lead section.

Musiconeologist (talk) 19:45, 29 August 2021 (UTC)


 * Update: From further searching it seems clear that my definition is indeed absolutely correct. The article's existing content seems to be paraphrased from several freely available research papers. They're also interesting examples of how fluctuation spectra can be useful, though they do need to be explained clearly. (What is fluctuating? What is a fluctuation spectrum in that context? What does it tell us?) I think the whole article needs rewriting. If nobody has any objections, I'll set about doing that. Musiconeologist (talk) 01:56, 8 September 2021 (UTC)

Proposed redirect
As far as I can tell, "Fluctuation Spectrum" is just a synonym for the Fourier decomposition of any periodic effect. I think it would make more sense to simply redirect this page to Fourier Transform, rather than try to establish independent notability of the term. Absent any objection, I'll make the redirect myself after a reasonable time for comment. PianoDan (talk) 19:10, 8 December 2021 (UTC)
 * Thinking about the target, I think Spectral Density might be a bit more specific, but there's still nothing at THIS article that's not covered better elsewhere. PianoDan (talk) 19:20, 17 December 2021 (UTC)