Talk:Frequency

message: Is it not true that the A tuning note is only 440 Hz in the United States, while in fact 442 Hz in Europe?  Perhaps this should be changed. — Preceding unsigned comment added by Trhaynes (talk • contribs) 18:27, 3 December 2004 (UTC)
replies: text: See Pitch (music) — Omegatron 14:36, 20 February 2006 (UTC)
thread_title:  440 Hz 

message: We have a rather strange paragraph that tells us how to measure frequency by dividing one number by another which is of course true. But do we have anything about various classes of frequency meter - i.e. how we actually measure frequency? Pcb21 Pete — Preceding undated comment added 10:54, 17 April 2006 (UTC)
replies: text: Yes, that would be a good addition, aince there is no separate article for that topic. --ChetvornoTALK 19:52, 8 August 2008 (UTC)
thread_title: Measurement

message: In my opinion, this is not a unit of frequency, but of angular frequency.
--84.159.248.246 17:04, 20 November 2006 (UTC)
thread_title:  radians per second 

message: I removed the non sequitur "Notes" heading and its entry about the human heartbeat being close to one Hertz. Actually, the human heartbeat varies quite a bit--it can get down to 0.8 Hertz in mellow marathoners and up to 2 Hz in times of high stress activity. Average heart rate is about 72 bpm, or 1.2 Hz. No studies support the statement that the heartbeat is exactly 60 beats per minute which means there's no benefit to the reader by announcing that the heartbeat is approximately 1 Hz. It doesn't shed any light on the concept of frequency. Binksternet (talk) 08:36, 25 January 2008 (UTC)
thread_title: Human heartbeat

message: Mean zero up-crossing period, TZ or Tm0,2
When recordings were first taken this was onto charts and simple counts could be made.  First the charts were zero-meaned (the average and trend calculated and drawn through the plot to provide a new axis for measuring) and then the number of times the wave record crossed the mean going up (or sometimes down) was counted and this gave the number of waves and, as a time measure, the zero-crossing period. The parameter is estimated by taking the mean of these periods for a given wave record.  For wave records on paper the mean level is found by eye and Tvisual  is estimated from the record length and the number of zero up-crossings counted on the record. This method can also be applied to digitised data using a computer but if the wave records are available in machine readable form it is preferable to estimate from the moments of the spectrum using,
	 Tz=sqrt(m0/m2)
where the mi values are spectral moments.  The alternative symbol of Tm0,2 is derived from the moment equation. It can be seen that TZ is very dependent on the higher frequency end of the spectrum and although TZ  is the most commonly used period estimator it is not very stable.
Significant wave period, Ts
The significant wave period is the mean of the zero up-crossing periods associated with the highest one third of the waves. It is sometimes denoted by Ts.  Note that this parameter cannot be obtained directly from the wave spectrum.  It is not very useful, but sometimes is used!
Spectral peak period, Tp
The spectral peak period is the inverse of the frequency at which the value of the frequency spectrum is a maximum.  It cannot be defined satisfactorily in multi-peaked spectra.  fp is very important in characterising spectra.
Period associated with the most likely highest wave, Tmax
The most likely height of the highest wave in a record of duration 3 hours is Hmax  and Tmax is its period.  It is often obtained indirectly from Tz or Tp  using empirical relationships, or from Hmax and steepness assumptions – usually to obtain a range of possible associated periods.  These methods should be applied only in the water depth for which the empirical relationships have been found, usually deep water (i.e. depth >1/2 wavelength).  It should be possible to use the steepness method in shallow water provided that refraction is minimal and that allowance can be made for shoaling effects.  It cannot, however, be derived directly from the wave spectrum.
Energy period, Te
This period is important for power estimation and is used in wave power design as a preferred comparator.  The most appropriate way to consider energy period is as the period of the regular wave that has the same significant height and the same power density as the sea-state under consideration.  It is defined as,
	 Te=(m-1/m0)
Because of the relationship with power it is worth giving the expression for time averaged power associated with a spectrum,
	 power = rho g^2 m0 Te / 4Pi
Hence we can find an expression for Te as follows,
	 Te=(64 Pi Power)/ rho g^2 Hs^2
Average wave period, Tav
 
This is the inverse of the average frequency calculated from the mean of all component sine waves weighted by the spectral energy.  It cannot be measured in the time domain unless the waves are simple sine curves.
Average crest period, Tc
Defined as,  Tc=sqrt{(m2/m4)}
This is equivalent to dividing the length of the wave record by the number of crests where a crest is any point either side of which the surface elevation decreases.  Crests are not necessarily associated with zero up-crossings.  Clearly this is very much influenced by the ‘tail’ of the spectrum through the fourth moment.
(copied from Talk:Wave period by Kraaiennest (talk) 21:46, 10 February 2008 (UTC)
thread_title: Period estimators (for [[ocean surface wave]]s, copied from [[Talk:Wave period]]

message: I have removed the following from the "Definitions and units" section:
:Frequency is important in wireless communications, where the frequency of a signal is mathematically related to the wavelength. If f is the frequency of an electromagnetic field in free space as measured in megahertz, and w is the wavelength as measured in meters, then w = 300/f and conversely f = 300/w
(1) The text, if it belongs in the article at all, is in the wrong section.  The text does not belong here.  There is a long list of things for which the concept of frequency is important, we aren't going to talk about all of them in the "definitions and units" section.  (2) The text is true but not true enough: (2a) With waves speed is always "mathematically related" (i.e. equal to the product) to frequency and wavelength, that fact is not specific to "wireless communications".  (2b) The 300 used is the speed of light in a vacuum, although we neglect to mention that point, but this isn't the page for quick rule-of-thumb formulae for radio technicians.  (2c) Elementary maths gives us one formula from the other so, once again, not useful here.  (3) Everything is already covered in the "physics of light" example section.
Paul Beardsell (talk) 19:22, 15 March 2009 (UTC)
thread_title:  Wireless communications 

message: I think most of the 'Physics of sound' section should be removed. Description of longitudinal vs. transverse waves, polarization, etc. are not necessary for the explanation of frequency of sound waves, and simply repeat coverage in other articles.   This is where 'Wikipedia bloat' comes from.  All that should appear is a simple exposition of sound wave frequency, mention of how it's measured, and maybe something on the 'spectrum' of sound frequencies analogous to the spectrum of electromagnetic waves.  --ChetvornoTALK 22:58, 17 March 2009 (UTC)
replies: text: I couldn't disagree more. There are far too many articles on audio equipment and acoustics and music that link to this page expecting it to explain what frequency has to do with sound. I recently added information about pitch, because it wasn't there and I needed it.--Atlantictire (talk) 03:04, 1 May 2011 (UTC)
replies: text: Done.  But see new section below.  Dicklyon (talk) 17:55, 18 January 2014 (UTC)
thread_title:  Put 'Physics of sound' section on a diet 

message: The last citation link links to xkcd for absolutely no reason.  —Preceding unsigned comment added by 71.228.164.178 (talk) 02:25, 9 June 2009 (UTC)
replies: text: No. Firstly, assume good faith. Secondly, xkcd is a comic (singular) and not a corporation, team or trained knowledge-fighting force all bent on destroying wikipedia. 217.23.232.41, you have yourself proven to be attributing more troll-like behaviour, having recently launched your own "one soldier counter offensive" and posting anti-xkcd pseudo rants on all talk sections of articles pertaining to or mentioned by the webcomic. I'm not in favour of more xkcd refs on WP, I'm just wondering who really has the problem here. --PenguinCopter (talk) 10:15, 12 June 2009 (UTC)
thread_title: Vandalism

message: Frequency in Fourier analysis is a different concept from 1/(period).  I don't have time to write an explanation now but I think that concept, and links to appropriate articles, would be helpful here.  Ccrrccrr (talk) 23:25, 19 February 2010 (UTC)
thread_title:  Fourier analysis 

message: Please add some data to the article saying what variables of waves in sound and light depend on the frequency of the wave.
eg speed, impedance, refracting index, attenuation coefficient, etc.  —Preceding unsigned comment added by 91.99.166.67 (talk) 10:50, 10 May 2010 (UTC)
thread_title:  It depends! 

message: Prior content in this article duplicated one or more previously published sources. The material was copied from: http://www.wavesignal.com/Light/index.html (content was added in February 2009; archives confirm their prior publication. Infringing material has been rewritten or removed and must not be restored, unless it is duly released under a compatible license. (For more information, please see "using copyrighted works from others" if you are not the copyright holder of this material, or "donating copyrighted materials" if you are.) For legal reasons, we cannot accept copyrighted text or images borrowed from other web sites or published material; such additions will be deleted. Contributors may use copyrighted publications as a source of information, but not as a source of sentences or phrases. Accordingly, the material may be rewritten, but only if it does not infringe on the copyright of the original or plagiarize from that source. Please see our guideline on non-free text for how to properly implement limited quotations of copyrighted text. Wikipedia takes copyright violations very seriously, and persistent violators will be blocked from editing. While we appreciate contributions, we must require all contributors to understand and comply with these policies. Thank you.  Moonriddengirl (talk) 21:43, 22 December 2010 (UTC)
thread_title:  Copyright problem removed 

message: Somewhere between 1,000 and 4,500 people visit this page every day. I think it might be useful to take a look at the pages that link here to try and get a sense of what the readers' needs are, and then to expand the lead so as to better orient them. It's nice after you've clicked on a link to a page to know from the lead why you're there. As someone who's just started learning about audio engineering concepts, I have to say I couldn't tell right away what frequency had to do with anything... and then I figured it out and added information about pitch. Yes, some of us really are that dumb!:)--Atlantictire (talk) 02:58, 1 May 2011 (UTC)
thread_title: Why are people coming to this page?

message: So what is the criterion for using f instead of the Greek letter ν? As far as I know ν is a more widely used symbol for frequency.  — Preceding unsigned comment added by 188.83.90.251 (talk) 16:10, 12 June 2011 (UTC)
replies: text: The relative frequency of usage of f and ν varies across different disciplines.  Dicklyon (talk) 17:19, 12 June 2011 (UTC)
replies: text: I added a mention of ν. Fgnievinski (talk) 16:14, 21 October 2014 (UTC)
thread_title:  ''f'' versus ''ν'' 

message: I reworked these old sections by departed User:Logger9, and renamed them to be just Light and Sound, since they're supposed to be about frequency, not about physics.  It's interesting that the sound one says "Frequency is the property of sound that most determines pitch," which is true for repetitive sound waves according to the definition of frequency given, but completely misses the opportunity to address the oft-discussed disconnect between frequency and pitch in psychoacoustics.  Project for another time...  Dicklyon (talk) 17:58, 18 January 2014 (UTC)
thread_title:  Physics of light and physics of sound 

message: Rename to Temporal frequency and keep Frequency as a redirect here. Not asking to change the scope of this article, just to have its title reflecting the scope more accurately. Thanks. Fgnievinski (talk) 16:16, 21 October 2014 (UTC)
replies: text: My feeling is that's not necessary.  "Temporal frequency" is the most common meaning of "frequency" and the other common meanings can be distinguished in the introduction, and for less common there's the hatnote directing readers to the DAB page.  I think it's irritating to readers to use some obscure term for the article title, and it makes it hard to link to the article.   From WP:NC the title chosen should be the one  "...that readers are likely to look or search for and that editors would naturally use to link to..." --ChetvornoTALK 18:16, 21 October 2014 (UTC)

text: I agree with 's assessment and recommendation. That said, I've created a redirect at Temporal frequency to the disambiguation page as its Lead clearly differentiates the term. --SCalhotrod (Talk) ☮ღ☺ 18:55, 17 November 2014 (UTC)
replies: text: Frequency is a concept based on occurrences over time, so the adjective temporal (of or related to time) is not needed, redundant. Binksternet (talk) 20:59, 17 November 2014 (UTC)
replies: text:  Binksternet's misunderstanding is exactly the reason why I proposed the renaming. Frequency may have originally started as synonym of temporal frequency, but it's outgrown that definition, e.g., spatial frequency is obviously a non-temporal type of frequency. Fgnievinski (talk) 21:41, 17 November 2014 (UTC)
replies: text: I agree that the word frequency came from frequent, which has long been a temporal phenomenon. The idea of something being frequent in time was borrowed by science to construct the much more recent idea that "spatial frequency" is not about time but about occurrences over area.  As such "spatial frequency" is relatively unimportant; a small percentage of humanity uses the term. (It appeared first in 1878 in a study of hemophiliacs, talking about their prevalence in a population or geographic area; the term was quickly criticized for its inaccuracy.) So you'll forgive me for protecting the much more common use. Binksternet (talk) 21:57, 17 November 2014 (UTC)
replies: text: I'll forgive you.  The temporal is the usual meaning, and no qualifier is needed.  Dicklyon (talk) 02:56, 18 November 2014 (UTC)
thread_title:  Renaming 

message: As per :wikt:frequency, the first definition of frequency is "The rate of occurrence of anything; the relationship between incidence and time period [or interval]" -- there's nothing about periodic/oscillating/cyclic in it, it's just the ratio of incidence count over time duration. Fgnievinski (talk) 06:57, 19 July 2015 (UTC)
replies: text: Perhaps the article Periodic function is already what you would split off?Constant314 (talk) 13:50, 19 July 2015 (UTC)
replies: text:  If you agree with re-targeting the redirects at wave frequency and wave period, then a hatnote in frequency would mostly settle the matter; in the reciprocal second article, a clear distinction between periodic and aperiodic frequency units is sourced to the BIPM. Fgnievinski (talk) 21:24, 19 July 2015 (UTC)
thread_title:  Split wave frequency 

message: I don't see the need for doing this.  The article is not particularly large, nowhere near splitting size, and the Measurement section itself is not large. --ChetvornoTALK 04:59, 23 July 2015 (UTC)
thread_title:  Splitting off Measurement section into new [[Frequency measurement]] article 

message: ===Electromagnetic radiation===
==== Radio waves and microwaves ====
Radio waves and microwaves are electromagnetic waves, consisting of spatially orthogonal electric and magnetic fields oscillating together in both time and space, traveling through space. The wavelengths are in the range of many meters to a few millimeters, corresponding to frequencies that can be directly measured in the time domain by observing the electrical signals induced in an antenna detecting the waves.
==== Light ====
Visible light is also electromagnetic radiation with much shorter wavelength, in the 400 to 700 nm range.  In scientific observations, it is detected as a stream of massless elementary particles called photons, each with an energy conventionally in the range 2.9 to 4.6 electronvolts.  (At low light intensities, these particles can be individually counted by a sufficiently sensitive photodetector.)  In common with other subatomic particles, even massive examples such as cold neutrons, streams of multiple photons arrive at detectors in spatial distributions that reflect wave-like propagation, displaying interference and diffraction. Hence a wavelength associated with any particle of such type can be directly measured using an interferometer. This applies also to massive particles such as neutrons.
From the measured wavelength and speed of photons, what is conventionally called a "frequency" can be calculated in the usual way:
:\displaystyle f=c/\lambda
where c is the speed of light (c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.  
Regarding the interpretation of these quantities, Feynman provided the following advice: 
 We cannot say whether light is particle or wave. This is not an either/or situation; light seems to be both particles and waves and thus is probably neither. 
Visible light shares that duality with, e.g., cold neutrons, the "frequency" of which is rarely mentioned.
Layzeeboi (talk) 07:36, 12 February 2017 (UTC)
replies: text: In an electromagnetic wave, the electric and magnetic fields don't have "a relative phase of 90°". The vectors are orthogonal, but the electric and magnetic fields are in phase; the peaks occur simultaneously (in most circumstances; in materials with an imaginary index of refraction they can be out of phase).  On your addition, my feeling is that the subject of the wave/particle nature of light is a little WP:OFFTOPIC for an article on frequency, although it probably doesn't hurt. Cheers. --ChetvornoTALK 16:12, 12 February 2017 (UTC)
replies: text: Thanks for catching the error. I feel that duality, in common with cold neutrons, is topical here as a caveat that wavelike properties constitute no guarantee that frequency is meaningful. Layzeeboi (talk) 00:16, 13 February 2017 (UTC)
replies: text: I don't understand that point, nor what change you are proposing to make to the article.  What does it mean for frequency to be "meaningful"?  When is it not? Dicklyon (talk) 01:55, 13 February 2017 (UTC)

text: My proposed text consisting of two subsections to replace the "Light" subsection appears above, embedded in this talk section.  By "meaningful", I mean treated as such by the cited sources. For example, cold neutrons show wave-like behaviour, but the sources cited there don't consider frequency. I think it can be helpful to reveal not only the meaning of a concept, but also its limitations. Layzeeboi (talk) 08:14, 16 February 2017 (UTC)
thread_title:  Examples 

message: ==== Radio waves and microwaves ====
Radio waves and microwaves are electromagnetic waves, consisting of spatially orthogonal electric and magnetic fields oscillating together in both time and space, traveling through space. The wavelengths are in the range of many meters to a few millimeters, corresponding to frequencies that can be directly measured in the time domain by observing the electrical signals induced in an antenna detecting the waves.
==== Light ====
Visible light is also electromagnetic radiation with much shorter wavelength, in the 400 to 700 nm range.  In scientific observations, it is detected as a stream of massless elementary particles called photons, each with an energy conventionally in the range 2.9 to 4.6 electronvolts.  (At low light intensities, these particles can be individually counted by a sufficiently sensitive photodetector.)  In common with other subatomic particles, even massive examples such as cold neutrons, streams of multiple photons arrive at detectors in spatial distributions that reflect wave-like propagation, displaying interference and diffraction. Hence a wavelength associated with any particle of such type can be directly measured using an interferometer. This applies also to massive particles such as neutrons.
From the measured wavelength and speed of photons, what is conventionally called a "frequency" can be calculated in the usual way:
:\displaystyle f=c/\lambda
where c is the speed of light (c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.  
Regarding the interpretation of these quantities, Feynman provided the following advice: 
 We cannot say whether light is particle or wave. This is not an either/or situation; light seems to be both particles and waves and thus is probably neither. 
Visible light shares that duality with, e.g., cold neutrons, the "frequency" of which is rarely mentioned.
Layzeeboi (talk) 07:36, 12 February 2017 (UTC)
replies: text: In an electromagnetic wave, the electric and magnetic fields don't have "a relative phase of 90°". The vectors are orthogonal, but the electric and magnetic fields are in phase; the peaks occur simultaneously (in most circumstances; in materials with an imaginary index of refraction they can be out of phase).  On your addition, my feeling is that the subject of the wave/particle nature of light is a little WP:OFFTOPIC for an article on frequency, although it probably doesn't hurt. Cheers. --ChetvornoTALK 16:12, 12 February 2017 (UTC)
replies: text: Thanks for catching the error. I feel that duality, in common with cold neutrons, is topical here as a caveat that wavelike properties constitute no guarantee that frequency is meaningful. Layzeeboi (talk) 00:16, 13 February 2017 (UTC)
replies: text: I don't understand that point, nor what change you are proposing to make to the article.  What does it mean for frequency to be "meaningful"?  When is it not? Dicklyon (talk) 01:55, 13 February 2017 (UTC)

text: My proposed text consisting of two subsections to replace the "Light" subsection appears above, embedded in this talk section.  By "meaningful", I mean treated as such by the cited sources. For example, cold neutrons show wave-like behaviour, but the sources cited there don't consider frequency. I think it can be helpful to reveal not only the meaning of a concept, but also its limitations. Layzeeboi (talk) 08:14, 16 February 2017 (UTC)
thread_title: Electromagnetic radiation

message: Visible light is also electromagnetic radiation with much shorter wavelength, in the 400 to 700 nm range.  In scientific observations, it is detected as a stream of massless elementary particles called photons, each with an energy conventionally in the range 2.9 to 4.6 electronvolts.  (At low light intensities, these particles can be individually counted by a sufficiently sensitive photodetector.)  In common with other subatomic particles, even massive examples such as cold neutrons, streams of multiple photons arrive at detectors in spatial distributions that reflect wave-like propagation, displaying interference and diffraction. Hence a wavelength associated with any particle of such type can be directly measured using an interferometer. This applies also to massive particles such as neutrons.
From the measured wavelength and speed of photons, what is conventionally called a "frequency" can be calculated in the usual way:
:\displaystyle f=c/\lambda
where c is the speed of light (c in a vacuum, or less in other media), f is the frequency and λ is the wavelength.  
Regarding the interpretation of these quantities, Feynman provided the following advice: 
 We cannot say whether light is particle or wave. This is not an either/or situation; light seems to be both particles and waves and thus is probably neither. 
Visible light shares that duality with, e.g., cold neutrons, the "frequency" of which is rarely mentioned.
Layzeeboi (talk) 07:36, 12 February 2017 (UTC)
replies: text: In an electromagnetic wave, the electric and magnetic fields don't have "a relative phase of 90°". The vectors are orthogonal, but the electric and magnetic fields are in phase; the peaks occur simultaneously (in most circumstances; in materials with an imaginary index of refraction they can be out of phase).  On your addition, my feeling is that the subject of the wave/particle nature of light is a little WP:OFFTOPIC for an article on frequency, although it probably doesn't hurt. Cheers. --ChetvornoTALK 16:12, 12 February 2017 (UTC)
replies: text: Thanks for catching the error. I feel that duality, in common with cold neutrons, is topical here as a caveat that wavelike properties constitute no guarantee that frequency is meaningful. Layzeeboi (talk) 00:16, 13 February 2017 (UTC)
replies: text: I don't understand that point, nor what change you are proposing to make to the article.  What does it mean for frequency to be "meaningful"?  When is it not? Dicklyon (talk) 01:55, 13 February 2017 (UTC)

text: My proposed text consisting of two subsections to replace the "Light" subsection appears above, embedded in this talk section.  By "meaningful", I mean treated as such by the cited sources. For example, cold neutrons show wave-like behaviour, but the sources cited there don't consider frequency. I think it can be helpful to reveal not only the meaning of a concept, but also its limitations. Layzeeboi (talk) 08:14, 16 February 2017 (UTC)
thread_title:  Light 

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thread_title:  External links modified 

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message: Hi, see it implicitly means 1 event, and 1 here is full of meaning, but (number of) event has no dimension, because it is a number. So Hertz not means "one per second", but it means "one event per second", i.e., one (or 1) here, is full of meaning. Hertz does not mean 1 "kilometer" per second or one "kilogram" per second or anything else, it means one "event" per second. Hooman Mallahzadeh (talk) 16:14, 30 December 2021 (UTC)
thread_title:  Hertz