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This article gives equations to find the speed of sound, is there any definite measure of the speed in miles per hour or kilometers per hour? [I used to think it was 1400 mph].
--Nathan
A site by NASA gives the speed of sound as 741 MPH
(talk • contribs) 19:01, 2 July 2008 (UTC)
The proper term is "speed of sound", not "velocity of sound." Velocity refers to a vector, but sound is characterized by a scalar: the speed of sound waves in a material, independent of direction. In some materials, sound travels faster in some directions than others, but even in such circumstances it is not characterized (AFAIK) by a vector. -- CYD
Does anyone have a reference for the claim that speed of sound varies linearly with temperature in air? As far as I know, this is not correct. My "standard atmosphere" table shows it varying strictly with the square root. I believe the linear expression should be removed from the page. -- User:wtph
To simplify, speed propagates due to the movement of the molecules that make up the gas, and thus speed of sound is proportional to the average speed of the molecules. Temperature is a measure of energy (which is proportional to the square of the velocity). Thus Speed is proportional to square root of energy and thus proportional to square root of temperature. (Understanding this then allows us to determine what effect molecule size will have. Larger molecules have higher mass and thus for the same energy have lower velocity. Thus speed of sound in gases with higher molar mass have lower speed of sound). -- Jon Ayre 14:20 9th Dec 2005 (GMT)
331.5+0.607*T(degrees celsius) meters/second. -- Monohouse 2006
The linear formula commonly used for the speed of sound as a function of temperature is the first-order approximation of the square root formula. In other words, it gives the tangent line approximation to the parabola using zero degrees Celsius as the point of tangency. For temperatures between -40 and 40 degrees Celsius, the linear approximation is within 1 m/s of the square root formula. The errors increase as the temperature gets farther from 0. Richard Hitt Feb 2006
So why don't we include this formula instead of the approximation? It's not that much more difficult...
Jesse 14:59, 21 June 2006 (UTC)
--62.167.176.34 (talk) 21:22, 2 November 2008 (UTC)
Might be stupid, but I was wondering whether the speed of sound actually is the maximum speed that "pressure" can travel through matter. If that is true, we should include it in this article...
Pressure is considered a state variable, so talking about the "speed of movement of pressure" doesn't mean a whole lot. Pressure doesn't "move" from one point to another.
As an explanation to a layman who may not know what a state variable is, one could accurately say the following: if you had a room with totally uniform pressure and then paused time, and you magically increased the pressure at one point in the room and then started time again, that pressure would "travel" at the speed of sound. To be more accurate, one would say that a wave of pressure would travel at the speed of sound.
When are relativistic effects important??? Should that part be removed?
Cosmologists now consider sound waves important in their description of the Big Bang. They have discovered that the equations governing sound are actually very useful to them in explaining the small variations they've observed in the 2 deg Kelvin cosmic microwave background.
They think that since the primordial universe was a liquid-like blob at extreme temperature and pressure shortly after the Big Bang, sound waves would have been able to (and did) propogate within it. The early universe supposedly also inflated faster than the speed of light. So relativistic effects would certainly be important in any detailed consideration of the baby universe. It's not trivial issue, either; those very minor differences in the pressures here and there in that early fireball created the universe we see today.
Other than that...I would think that any theoretical physicist who'd done enough serious drugs in high school that he decided to work out how fast a 'knock knock' joke would move inside a spinning neutron star (whose surface can be racing along at about 1/7th of the speed of light) would definitely need to take relativity into account. 66.11.164.72 03:48, 10 March 2006 (UTC)
Shouldn't that be a rise in pressure that causes condensation? Or alternatively, a drop in pressure accompangnied by an even larger drop in temperature as a result of adiabatic cooling?
I feel that the caption to this photo is somewhat misleading. It associates the observed Prandtl–Glauert singularity with "breaking of the sound barrier" even though this effect can be observed with aircraft traveling at subsonic speeds. <http://web.archive.org/web/20070510225616/www.fluidmech.net/tutorials/sonic/prandtl-glauert-clouds.htm>
Removing the grain kind of ruins the picture. It's going to be downsampled anyway, so it's unnecessary. But the highly filtered one we have now makes the condensation look fake and plastic, where simple downsampling gives a much more nuanced picture. Unless I hear objection I'm going to remove the filtered version and replace it with the original. (There's no reason to be doctoring this photo.) Gerweck (talk) 18:36, 31 March 2012 (UTC)
This is news to me. I thought sound travelled faster in high density air.
I've added this new section, because I think it's important to note that sound also moves through media other than gases, like air. I was tempted to add the following two paragraphs to the same section, but first I would like to get some feedback. For sure they involve speed; the potential issue is whether or not they involve sound. I will leave that question to the knowledgeable jurors here:
Seismic waves generated by earthquakes are analogous to sound waves in air. Both involve compression and rarifaction of the media they are passing through. Thus the shock waves generated by an earthquake can be thought of as sound waves moving through the Earth. However, since the predominant frequency of the energy is only about 1 Hz, or lower, it's well below the audible threshold of about 20 Hz. Thus it is considered to be a pressure wave. The science of studying these waves is known as seismology.
Density of matter within the Earth increases greatly with depth, so the velocity of pressure waves is also considerably higher deep inside our planet. At extreme depths, near the Earth's core, shock or pressure or sound waves move very supersonically, at speeds as high as Mach 20 to 25, or about the velocity of the space shuttle on re-entry. Pressure waves can easily move from one quadrant of our planet to another - from China to Africa - in less than 15 minutes. Stellar-TO 22:50, 11 November 2005 (UTC)
Meme is not a word I can find in my dictionary, guy! Take a memo: please expunge that non-existent word from your brain. :)
I don't think the issue is as simple as grade school arithmetic, like you seem to believe it is. One almost has to be a physicist to understand it. I am not a physicist, but let me try to clarify.
Let's deal with the case of sound in a fluid, which much of the inner planet is, in the case of the quite large outer liquid core. See: Bulk modulus. According to that article, the adiabatic bulk modulus K is approximately given by K = aP where a is the adiabatic index and P is the pressure. In solids, Young's modulus is also measured in terms of *pressure*.
So, speed of a sound wave (or seismic shock wave, which is equivalent) in liquids or solids is proportional to the *pressure*. That is the accurate way to put it, excuse me all to heck. Increasing pressure means increasing speed. If the adiabatic bulk modulus goes up, or Young's modulus goes up, speed of the propogated energy also goes up.
However. What you have apparently ignored is that increased pressure also implies increased *density*. Which really means that density is also on the TOP part of the equation, as well as on the bottom. You cannot see it there, I know, but it is there. It's the difference between citing equations, and understanding them.
Or do you believe that putting materials under enormous pressure - like the roughly 3.5 million atmospheres at the center of the earth - will NOT squish things into a more dense state?
The average density of our planet is about 5.5 gm/cm^3. Estimated densities in gm/cm^3 are: crust: 2.2, upper mantle 3.4, lower mantle 4.4, outer core 9.9, inner core 12.8 - 13.5. The inner core is more dense than lead, which is only 11.3 gm/cm^3. It's roughly 13 times more dense than water.
That is why sound - or a shock wave - moves through it *very* fast! It's very *dense*. Don't say NO NO NO...because your brain has looked at only HALF the equation, the bottom part. (Where density appears, formally.) You have to look at the TOP part, too. What does ENORMOUS PRESSURE imply? It implies a change in density, to greater. Yeah? Yeah. So...increasing pressure means increasing density...means speed goes *UP*.
Pressure dictates the speed, but it also dictates density! They are *both* linked to it. If pressure goes up...they both go up. Right?
So...effectively...in the equation for the speed of sound, in solids or liquids: density is in the TOP part of the equation, too. Because *pressure* is there! That's why it's not entirely accurate to allege that speed *decreases* with density, if you're talking about the inner planet. Which is what I was talking about. You cannot vary the pressure without varying density, as well.
So I say again: speed goes *UP* with density!!! Not *DOWN*, you sonic infidel. But I admit: the governing reason is the *PRESSURE*. There. I am so profoundly grateful to you for inspiring me to clarify my somewhat clumsily inadquate point. Excuse me, and thank you! :) 66.11.164.72 01:55, 10 March 2006 (UTC)
Should we add a section on the classic methods for the measurement of the speed of sound (for instance Kundt's tube) ? Cadmium 14:14, 1 January 2006 (UTC)
If you divide the universal gas constant by the molar mass of a specific gas, you cannot possibly end up with the universal gas constant again. Many people call that a "specific gas constant", some may have other names, but "universal gas constant" is positively wrong. Unfortunately, the current gas constant article adds to the confusion, I'll take the issue there as well. Algae 20:14, 1 January 2006 (UTC)
May I support this point: at least for physicists, there is only one universal gas constant R: the Boltzmann constant times the Avogadro number. The use of an air-specific constant R in this article is highly confusing and should be avoided. Please replace R by R/M and adjust the explanation. The resulting formula would apply to arbitrary (degrees of freedom, molar mass) ideal gases. Nils Blümer 20:13, 3 February 2006 (UTC)
The first paragraph of this sound article states clearly that static pressure has no effect upon the speed of sound. This is patently false, which I can vouch for as a physicist myself. Go get any elementary college physics text and you'll see that this is false. For example, I'll dig one up for you: look at Physics, 2nd ed., by Ohanian. Chapter 17, equation (3) clearly states that, "...the theoretical formula for the speed of sound is Vs = root(1.4*Po/po), where Po and po designate the UNPERTURBED [i.e. static] PRESSURE AND DENSITY, respectively." On top of this fact, this article itself then gives equations at the bottom of the page in terms of air pressure. Another problem, the incorrect sentence writes Static Pressure (Air Pressure) as if the two were the same thing, but if you read both articles you see that they are not. I'm deleting the error in the first paragraph; if you revert my corrections, please for the sake of all that is proper physics provide your sources. Thanks Astrobayes 21:27, 18 March 2006 (UTC)
The intro paragraph stresses how important temperature is on the speed of sound, but is never brought up in the analogy used in the Basic concept paragraph. Using the ball/spring model it is easy to visualise why density plays a role, but why is temperature excluded? Is this because the analogy fails to explain it? Does the speed of sound vary with increased temperature because of the increased average vibration energy in a medium? How? I think the temperature effect needs to be addressed before beginning the math. --Daleh 14:41, 27 August 2006 (UTC)
I've been going 'round and 'round about this in the, Electrotech Forums (where I'm considered pretty much an ignorant pest). The "balls separated by springs" analogy (and its counterparts) seems to be very firmly ingrained in the minds of the physics world.
But, you're right, it doesn't even address the temperature issue (much less answer it). We are asked to believe, for example, that the repulsive force of neighboring molecules substantially changes with temperature and very little with how close they may be packed together. That the thin air at 30,000 feet and the denser air at sea level can have the same Mach number so long as their temperature is the same based...on the "stiffness" of the mutual repulsive force of the air molecules.
Eventually, I came up with a scenario that I believe at least addresses the temperature issue and reference it here for analysis:
http://www.electro-tech-online.com/math-physics/87198-why-does-sound-propagate-14.html
Start near the bottom of that pge wiht the post by, Crashsite titled, "Got It". Also see the next few following posts.
I have to say that there's still a piece missing. And, it's the same one that's missing from the "ball and spring" model. Exactly how a subsonic disturbance is suddenly and near instantly accelerated to Mach 1 and then propagated at that speed. Like, Daleh seems to, I suspect that it has something to do with the natural vibrational speed of the molecules due to temperature but, I haven't quite figured out just how and my math skills are too poor to deduce it that way. Crashsite55 (talk) 03:03, 28 May 2009 (UTC)
There is an inserted picture relating to the "sound barrier" of which there is no mention except at the bottom (see also). Is this picture for the 'thrill' factor ? Preroll (talk) 02:47, 14 October 2010 (UTC)
Should we use the speed of sound for 0 °C as 331.5 or 331.6 m/s?
Google shows 829 answers for 331.6:
http://www.google.com/search?&q=Speed+of+sound 331.6
Google shows 11,500 answers for 331.5
http://www.google.com/search?&q=Speed+of+sound 331.5
The answer seems very clear. --Tom 5:27, 28 September 2006 (UTC)
Don't trust Google as a source of info, for quite often it ends up reflecting errors in Wikipedia these days. Not too long ago I caught Wikipedia in an error on the number of spikes in the seed capsule in the American Sweetgum, a tree that lines the street where I live. Wikipedia said there were 40 to 60 capsules per gumball, each with 1 spike. In fact, there are twice that many spikes betcause there are TWO per capsule, as anybody can verify by simply counting them (there are about 100). But the wrong information (which included several recent texts) had spread from Wikipedia all across the net. We changed it, and now the correct numbers are spreading in the reverse way. It's Stephen King's Word Processor of the Gods-- change the entry to change reality. Unless you want to go out to your yard and actually look for yourself, that is. SBHarris 19:32, 3 October 2006 (UTC)
I did some work in the early 90's on the speed of sound in air that was published in J. Acoust. Soc. Am., 93, p2510, 1993. I was working realizing a National Standard for sound pressure level by reciprocity calibration of reference condenser microphiones in South Africa. Beacuse our lab was at high altitude near Johannesburg(about 85kpa) we needed to take pressure into account. I started off using some work that had been done by George Wong of the NRC in Canada, who was doing the same type of work on microphones. However when trying to use Wong's values in my own calculation including pressure coefficients, I found some discrepancies. The above-referenced paper addresses the details. I note that it appears that the approximate formula that I generated was proposed for use in European Metrology Laboratories [K Rasmussen, 1997 Calculation methods for the physical properties of air used in the calibration of microphones]. Rasmussen was the chair of the IEC committee that was standardizing microphone calibration procedures. My value of the speed of sound in dry CO2 free air at 0 deg C was 331.45 m/s, and this was calculated using virial coefficients to account for departures of the gaseous constituents of standard air from Ideal gasses. I beleive that this accounted for the discrepancy between my work and the work of Wong, who had used some ideal gas values. I beleive that my work and other work supports a value of 331.45 or rounded up to 331.5, if this level of precision is required. [Owen Cramer, 20 Sept 2007]
Probable mistake: The stated Young´s modulus for Yttrium Iron Garnet, 2000 GPa, seems way off. In the wiki article on Young´s modulus it is stated as 193 GPa. The lower value appears in several places on the web, but I have only found the higher value in one place, where it is listed as 2*10^12. That is the webpage listed as reference #16, BTW. If that higher value were true, YIG would be four times as stiff as tungsten, and almost double the stiffness of diamond. —Preceding unsigned comment added by 83.209.73.77 (talk) 10:40, 15 January 2009 (UTC)
In a solid rod (with thickness much smaller than the wavelength) the speed of sound is given by:
where
Thus in steel the speed of sound is approximately 5100 m·s-1.
Would someone like to educate the human race as to what units this equation uses to derive this conclusion? Because try as I might, I can't figure it out. You divide GPa by kg/m3, take the square root, and somehow arrive at m/s ? Neat trick. —The preceding unsigned comment was added by 76.209.59.227 (talk) 04:32, 21 January 2007 (UTC).
I have never edited a page before, and am more happy to bring this up in the discussion. The article says that the Chen-Millero-Li Equation (1994) is more accurate than V. A. Del Grosso (1974). But in my research I came across a paper in the The Journal of the Acoustical Society of America that empiricaly showed Del Grosso is more accurate than Chen-Millero-Li. Article Abstract. Also stubled into this paper that show Del Grosso as being more accurate than Chen-Millero dushaw-jasa-93 71.39.95.25 21:26, 23 January 2007 (UTC)
Altitude of commercial jets. - Most jets fly much lower than 11000m. If you're on a short hop, you might be at 29,000 ft-31,000. For transatlantic flights, 35,000ft < 11000m.
According to p351 of Wood 1946 (who quotes from early work by Herzfeld and Rice) "... the adiabatic state is best guaranteed for the low frequencies, while for the higher frequencies the influence of heat conduction is larger ...". Unless this statement is challenged by more recent research I suggest the paragraph about frequency dependence be either deleted or reversed.
REF: A B Wood, A Textbook of Sound (Bell, London, 1946)
Thunderbird2 21:50, 8 July 2007 (UTC)
The speed of sound varies with the medium employed, as well as with the properties of the medium, especially temperature. The term is commonly used to refer specifically to the speed of sound in air. At sea level, at a temperature of 21 °C (70 °F) and under normal atmospheric conditions, the speed of sound is 344 m/s.
It makes no sense to give the speed of sound adding the words at the "standard atmosphere at sea level". We have the formula:
Statement: The air pressure p and the density ρ of air are proportional at the same temperature. That means, the fraction p / ρ is always constant, even at "sea level". Cross always the useless words "At sea level". If the temperature is the same, we get the the same speed of sound down at sea level and high on a mountain.
John 21:50, 5 September 2007 (UTC)
Can the speed of sound rise in above its original speed in air (or any substances for that matter)LearnguyLearnguy (talk) 17:09, 27 April 2008 (UTC)?
The opening paragraph says "...343 m/s. This also equates to 1235 km/h, 767 mph, 1129 ft/s" By my calculation, 343 m/s = 1125.328048 ft/s which is easily enough rounded down to 1125 ft/s. The mistake is probably the result of someone changing the reference to 343 m/s from a previous notation of 344 m/s. I will correct the f/s calculation. MRJayMach (talk) 14:08, 16 September 2008 (UTC)
The link to an article in New Scientist magazine (http://space.newscientist.com/article/mg19826504.200-did-sound-once-travel-at-light-speed.html?feedId=online-news_rss20) is frustrating as it leads to just the first few paragraphs of an article and then requires the reader to buy a subscription to read on. Such links serve commerce rather than the reader, and it seems to me that they are best avoided - or at least flagged as a tease. But before or rather than immediately deleting it I thought I should ask if other readers feel the same way... Sng
The “Basic Concept” section gives the following example:
All other things being equal, sound will travel more slowly in denser materials, and faster in stiffer ones. For instance, sound will travel faster in iron than uranium, and faster in hydrogen than nitrogen, due to the lower density of the first material of each set.
I'm pretty sure uranium is stiffer than iron, so the “all else equal” premise is not satisfied. The solids example might be replaced, for instance, with iron and carbon steel: the density should be similar, but the stiffness can vary widely.
It might also be a good idea to replace one of the gases such that they have the molecular structure. In this case, both hydrogen and nitrogen are diatomic, but the N–N link is rigid for torsion while the H–H link allows rotation. The article earlier mentions indirectly that the freedoms of the molecules is a factor, so this also violates the “all else equal” premise. I'm not sure that's very significant, but it's no big deal to replace nitrogen with any halogen (F, Cl), thus making sure that only the density changes.
I created a table in OpenOffice Calc with temperatures per degree from -30˚C +35˚C, using the formula 331.3 + 0.606 * C, and the numbers vary with the ones listed in the table at Speed_of_sound#Tables. They match at 0˚C and 5˚C, but already at -5˚C and at +10˚C, they vary. My numbers are available here. Should the wikipedia table be updated, or are my numbers wrong? Rkarlsba (talk) 11:42, 3 September 2010 (UTC)
I'm pretty sure that somewhere there's a bit about China Airlines Flight 006 "almost certainly" breaking the sound barrier, but I can't seem to find it. Can anyone help me out here? —Preceding unsigned comment added by 66.189.116.112 (talk) 23:42, 28 September 2010 (UTC)
Oh, and I forgot earlier, I think there was a part in the same section about a DC-8 also possibly breaking the sound barrier in a shallow dive during a test flight. Can't remember the date.66.189.116.112 (talk) 23:48, 28 September 2010 (UTC)
The introduction states that the speed of sound in iron is 5,120 m/s, and then in the next paragraph states that the speed of sound in solids depends on whether the wave is transverse or longitudinal. So when the "speed of sound" is stated for a solid material such as iron, as it was above, is there a convention as to which speed is the one being referred to? I would assume it's the longitudinal case, because the paragraph is comparing it with the speed in various fluids, which carry longitudinal waves only. --JB Gnome (talk) 22:54, 7 December 2010 (UTC)
The two speeds are equal only when Poisson's ratio is equal to zero. This is possible, as Poisson's ratio can take on values from -1 to +1/2 for materials. In a metal, where Poisson's ratio might typically be +1/3, the ratio of the speeds would be 2/3, meaning that the speed of sound is 50% faster in the bulk material than in the long, thin rod. I think this is right, but need to check before putting it in. Are there separate compression and sheer waves in a thin rod, or just one type of tangent-sheer wave? SBHarris 19:32, 28 July 2011 (UTC)
Does the plot in the Practical Formula section add value to the article? The green trace is an "Approximation of the speed of sound in dry air based on the heat capacity ratio" and the red trace is the Taylor series approximation. While it would be interesting to compare an approximation to the actual speed of sound, I don't feel it benefits the article to compare two approximations. All we're doing is showing that sqrt(1+x) ≈ 1+x/2, which not specific to the phenomenon of sound. Furthermore, the plot may mislead the reader that the green trace is accurate, even near absolute zero, where it's probably not. Spiel496 (talk) 21:42, 19 September 2011 (UTC)
How can the speed of sound be 1062 kph over the entire range of 11,000 to 20,000 m? I was hoping to be able to determine the speed of sound at the altitude where the sound barrier was first broken by a wheeled vehicle, namely 4000 feet, by interpolation from such a table (since lapse rate is essentially linear with altitude), but this table doesn't seem to serve that purpose. --Vaughan Pratt (talk) 18:26, 15 July 2012 (UTC)
How about a table of speed of sound in various mediums? Some of them are mentioned in the article, though. 85.217.39.114 (talk) 14:06, 30 July 2012 (UTC)
Shouldn't the intro sentence stating the speed of sound in dry air at a given temperature also specify the altitude (or, more specifically, air pressure) ? The speed of sound in a gaseous medium does change with pressure, right? I'm no physicist so I thought I'd post this here rather than make the edit myself. I'm assuming the speed given is at sea-level, but I'm not sure.
Thanks!
Spiral5800 (talk) 00:59, 27 September 2012 (UTC)
The section on Mach number is very confusing.
It gives a complicated formula for "computing Mach number." The formula for computing Mach number is actually very simple: Take your speed. Divide it by the speed of sound. That's the Mach number.
I suggest deleting everything in this section following the words "Mach number is a function of temperature," since it's not very relevant to the subject. People who want to know how to compute Mach number in the case that you know neither your speed nor the speed of sound should go to the article on Mach number.
Geoffrey.landis (talk) 16:00, 3 October 2012 (UTC)
The article currently gives the speed of sound in dry air, at standard temperature, as 343.2 m/s. This is both wrong and misleading in the precision claimed. This value appears to have been cooked up as follows. Take the adiabatic index to be 1.400, T=293.15 K, and the molecular weight of air to be 28.9644 g/mol (the value from the US Standard Atmosphere). Plugging in numbers gives 343.24 m/s. This is wrong because air contains traces of gases that are not diatomic, so the adiabatic index isn't exactly 1.4. The article itself cites measured values ranging from 1.3991 to 1.403, with the middle of the range being a little higher than the diatomic value, presumably because of the presence of monoatomic gases such as argon, and despite the presence of polyatomic gases such as methane. Taking the middle of the range for the adiabatic index gives 343.36 m/s, the low end of the range gives 343.11 m/s, and the high end of the range gives 343.60 m/s. It clearly doesn't make sense to take a molecular weight from the USSA, but use an adiabatic index that isn't consistent with the mixture of gases defined in the USSA. What this really demonstrates is simply that it's silly to try to give the speed of sound in dry air at standard temperature to a precision of a tenth of a meter per second. The experimental range of variation of the adiabatic index is enough to make this precision meaningless. This is presumably why one sees a variety of values floating around on the internet. My students seem to be finding 343.2 m/s (presumably from WP) and also 343.6 m/s. My students' naivete about significant figures isn't by itself a reason to delete this sig fig from the article, but the considerations above show that the digit is not in fact significant given the experimental state of the art, and in any case has been derived from an inconsistent set of assumptions. (Much bigger changes would also result from temperature changes of a fraction of a degree, or a tiny bit of humidity.) For these reasons, I'm going to delete the final sig fig from the article.--207.233.84.11 (talk) 19:26, 20 February 2014 (UTC)
Any value in adding a comment to the equations section that the letter "c" in the equations is based on the word "celerity"? (As opposed to using "v" for velocity). 99.245.230.105 (talk) 09:37, 8 March 2014 (UTC)
my response (sorry don't know how to annotate properly): This article is about speed, which is a scalar quantity, "velocity" is a vector, so there would be no need to use "v" or "velocity".
As to the original of symbols such as "c", this article talks about celeritas (Latin): http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/c.html
That page makes it clear that "c" was used because it's the first letter of "celeritas", but it also refers directly to the speed of light.
BTW, if someone does see fit to add a section about "celerity", please don't use "celerity" - use the correct Latin "celeritas".
However it also raises questions about the use of "c" for the speed of sound. "c" is most often used for speed of light, e.g. E=mc2, and I always thought it was reserved for that purpose, but apparently it is also used for the speed of sound (news to me). Perhaps discussion of the applicability of the symbol "c" is outside the scope of this article? Perhaps a separate article talking about the original of some of the symbols in use in Physics & Mathematics? — Preceding unsigned comment added by 69.196.132.83 (talk) 16:57, 21 June 2015 (UTC)
Someone should remake the equation images to remove the trailing "," (comma) and "." (period). I see they are also in the alt text expression. Those punctuation marks don't belong in the equations. It looks particularly bad for 273.15 - one occurrence has a "." above it and the other has it after the 5, i.e. "273.15." If you want to add punctuation to the article, e.g. commas between several items (equations?), then do it in the HTML markup, not in the equation images. In fact, I would not even put those commas and periods in the article, i.e. when listing several equations or including an equation in the narrative.
For example: https://upload.wikimedia.org/math/9/3/f/93fe3a13923fef7a15be23e5c7fb6fed.png — Preceding unsigned comment added by 69.196.151.159 (talk) 17:26, 21 June 2015 (UTC)
<math>
tags (which puts them in the equation image) or else weird formatting thing can happen. See MOS:MATH#PUNC. Mysticdan (talk) 21:42, 12 August 2015 (UTC)"In gases, adiabatic compressibility is directly related to pressure through the heat capacity ratio (adiabatic index), and pressure and density are inversely related at a given temperature and composition, thus making only the latter independent properties (temperature, molecular composition, and heat capacity ratio) important."
This sentence is confusing me, surely the heat capacity ratio is set by the molecular composition? For example (temperature and heat capacity ratio) would be ok, or (temperature and molecular composition) would be ok too, but having all three in there is seems wrong. Also, what's meant by "latter independent properties"? What makes them latter? Not edited myself because I'm not completely sure about it all.
According to the Method of style of Wikipedia this article should be stating values using the metric units first.
Unit choice and order — Preceding unsigned comment added by 99.241.73.202 (talk) 22:54, 12 March 2016 (UTC)
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Perhaps there is good reason for it, but the 2nd and 3rd equations in section "Practical formula for dry air" place the m/s units in the middle of the right-hand-side of the equation which just looks weird to me. Aren't units conventionally placed at the end of an expression? It also almost looks like the radical is under the slant division line which I don't think is the intent. I think the m/s should be moved to the end of both of these equations.
Mtbusche (talk) 21:42, 16 August 2016 (UTC)
Perhaps someone can edit this to make grammatical sense? The full sentence in the "Basic concepts" section currently reads:
"This is usually illustrated by presenting data for three materials, such as air, water and steel, which also have vastly different levels compressibilities which more than make up for the density differences."
Tonyfaull (talk) 13:19, 17 September 2018 (UTC)
I'd like to point out that the graph next to the MacKenzie formula does not correlate to a practical application of said formula.
C++ implementation
double SoundSpeedInSeaWater( double Celsius, double pptSalt, double mDepth ) // MacKenzie
{
double T = Celsius;
double T2 = T*T;
double T3 = T2*T;
double S = pptSalt;
double D = mDepth;
double D2 = D*D;
double D3 = D2*D;
return 1448.96 + 4.591*T - 5.304e-2*T2 + 2.374e-4*T3 + 1.340*(S-35)
+ 1.630e-2*D + 1.675e-7*D2 - 1.025e-2*T*(S-35) - 7.139e-13*T*D3;
}
Sample output from MacKenzie formula:
This table, at 25C and 3.5% salinity, shows that MacKenzie is always increasing..
Specifically, it lacks the minimum at the deep sound channel.
While the graph itself may be correct (e.g per UNESCO standard),
I do not think it should be placed next to an uncorrelated formula.
For now, I added a note that the graph does not depict the
MacKenzie formula, It might clarify the inherent confusion ?
Revision: I just realized that the discrepancy of the graph is due to
the fact I don't have the temperature data for the different depths.
For my own part, I'm tempted to do a least-squares curve fit against
the graph, knowing full well it will not fit all locations.
Just my penny to the pot.
Love Nystrom (talk) 14:18, 25 September 2018 (UTC)
At 0˚C/32˚F (worldwide standard), the speed-of-sound in air is ~332 meters per second, 1,195 km/h, 742.5 mph. 2601:580:10A:E108:DE6:F40A:E32C:69E9 (talk) 23:35, 13 December 2018 (UTC)
: "Worldwide standard"? According to who? 2601:589:4801:5660:2883:21C1:122A:78D5 (talk) 13:54, 17 June 2021 (UTC)
The section "Equations" says the speed of sound comes from derivative of pressure with respect to density "at constant entropy". This is ambiguous, since entropy is extensive and this derivative involves intensive quantities. It could be understood to mean constant entropy density, but that would be wrong. The standard assumption is that the compression is adiabatic, which means constant entropy per particle (in a system where the number of particles is a conserved quantity). I suggest it be edited to say this clearly.
Dark Formal (talk) 01:44, 7 April 2019 (UTC)
This reads odd: it paraphrases a Latin phrase (then links to the Latin expression), provides an uncited heuristic, and doesn't explain what "other things" are being held equal.
I think:
Holy crap my formatting attempt got slaughtered. Sorry about that. JackW2 (talk) 10:40, 23 January 2021 (UTC)
The derivation really sucked. I am wondering if it came from a Dr. Seuss coloring book? I had no idea his PhD was in physics until now. I fixed it a little, but I don't have time to do a real fix. The remaining problem is too serious for it to be worth it for me to fix given the chance of some revert by bigwigs here. I mean I could fix it but I'd use math I doubt you mods want here since it might be too advanced for whatever this page is for. (High school AP students?) If there's encouragement I'll consider it.
Anyways, the issue is the whole approach, but for one thing it assumes steady state for parts of a differentially accelerating compressible fluid/gas. Here's what it says now:
"Consider the sound wave propagating at speed through a pipe aligned with the axis and with a cross-sectional area of . In time interval it moves length . In steady state, the mass flow rate must be the same at the two ends of the tube, therefore ... Per Newton's second law, the pressure-gradient force provides the acceleration..."
If you need a laugh or don't get what I'm whining about, just click on the phrase steady state above. --Jason Arthur Taylor Jasontaylor7 (talk) 22:30, 28 March 2021 (UTC)
I added... At 0°C/32°F, the speed-of-sound is 1192 km/h, 741 mph.<ref]https://www.weather.gov/epz/wxcalc_speedofsound </ref] 2601:589:4801:5660:2883:21C1:122A:78D5 (talk) 13:58, 17 June 2021 (UTC)
Hey there, just passing by, but shouldn't Vincenzo_Viviani be mentioned in the history part? He got a very precise figure in 1656 (in October, so probably around 15-20°C, the 350m/s measured is just 5-10m/s off). | Link for reference. Feel free to add if you agree ; I probably won't see any answer posted here. Cheers, 81.249.166.253 (talk) 11:39, 14 June 2022 (UTC)
You reverted an edit which I made, saying that what I described was only a thought experiment.
No problem if I've violated the requirements but I'd have to take issue with "thought experiment". I did this personally in a physics lesson on the playing fields at Swanwick Hall Grammar School in 1964 when I was eleven years old. Perhaps I should find the physics textbook in use by the school at that time to give as a reference? However after almost 60 years I can't even be sure that the method is described in it. :)
Ged Haywood (talk) 14:01, 27 September 2022 (UTC)
Thanks for the explanation. We can leave it ther for now. You're right of course that the accuracy of the, er, method may leave something to be desired - potential sources of error are left as an exercise for the reader. :) — Preceding unsigned comment added by Ged Haywood (talk • contribs) 16:28, 28 September 2022 (UTC)
The lead uses "as fast" while Basic concepts uses "times faster", and both are used to mean the same thing (times the speed of). I don't know if either is preferred on the site, but it's inconsistent. I'd support changing all uses to "as fast" personally, but the issue is contentious so I'd rather not start an edit war. I'd at least like one phrasing to be used throughout the article. Zombiewizard45 (talk) 20:33, 25 July 2023 (UTC)
https://en.wikipedia.org/w/index.php?title=Speed_of_sound&curid=147853&diff=1244332649&oldid=1244329377 "When an aircraft is flying at Mach 1, it is not breaking the sound barrier or anything else. Once the first aircraft reached Mach 1 for the first time in 1947 the barrier was broken. That barrier no longer exists - it doesn’t have to broken again and again, every time an aircraft flies supersonically." Not being combative, but it seems to me that it would be a bit strong to say that nowadays nothing is broken when an aircraft passes through the speed of sound. True, the phrase 'sound barrier' was invented by a newspaper reporter, but I think that doesn't devoid it of physical meaning. The comment above by @Dolphin51: interprets the phrase as simply rhetorical, referring to something that seemed important in history. But it seems to me that it also has a physical meaning, referring to such things as transiently increased air resistance?Chjoaygame (talk) 19:21, 6 September 2024 (UTC)
An F/A-18 Hornet displaying rare localized condensation breaking the speed of sound. I changed the caption to remove the word “breaking” and replacing it with “at”. I doubt there would be much support for the expression
breaking the speed of sound. The first man-made attempts to accelerate objects to the speed of sound were unrelated to aircraft. For several centuries cannon balls, artillery shells, musket balls and rifle bullets have had muzzle velocities greater than the speed of sound, so there has been no barrier at the speed of sound.