Sound speed - the rate of propagation of elastic waves in the medium: both longitudinal (in gases, liquids or solid bodies) and transverse, shear (in solid bodies). It is determined by elasticity and density of the medium: as a rule, in the gases, the speed of sound is less than in liquids, and in liquids - less than in solid bodies. Also, in the gases, the sound speed depends on the temperature of this substance, in single crystals - from the direction of the wave propagation. It usually does not depend on the frequency of the wave and its amplitude; In cases where the sound speed depends on the frequency, they talk about the dispersion of the sound.

Encyclopedic YouTube.

Already in the ancient authors there is an indication that the sound is due to the vibrational movement of the body (Ptolemy, Euclidean). Aristotle notes that the sound speed has a finite value and correctly imagines the nature of the sound. Attempts to experimentally determine the speed of sound belong to the first half of the XVII century. F. Konkon in the "New Organon" pointed to the ability to determine the speed of sound by comparing the time intervals between the flash of the light and the sound of the shot. Applying this method, various researchers (M. Messenn, P. Gassendi, U. Derlam, the group of scientists of the Paris Academy of Sciences - D. Cassini, Picar, Guuygens, Römer) determined the value of the speed of sound (depending on the terms of the experiments, 350-390 m /from). Theoretically, the question of the speed of sound was first reviewed Newton in his "principles". Newton actually suggested the isotherness of the propagation of sound, so he received an understated rating. The correct theoretical value of the sound speed was obtained by Laplace. [ ]

Calculation of speed in liquid and gas

The speed of sound in a homogeneous liquid (or gas) is calculated by the formula:

C \u003d 1 β ρ (\\ displayStyle C \u003d (\\ SQRT (\\ FRAC (1) (\\ beta \\ rho))))

In private derivatives:

C \u003d - V 2 (∂ p ∂ V) S \u003d - V 2 C p c V (∂ p ∂ V) T (\\ displayStyle C \u003d (\\ SQRT (-V ^ (2) \\ left ((\\ FRAC (\\ (\\ partial v)) \\ right) _ (t))))

where β (\\ displaystyle \\ beta) is adiabatic compressibility of the medium; ρ (\\ displaystyle \\ rho) - density; C P (\\ displayStyle CP) - isobaric heat capacity; C V (\\ DisplayStyle CV) - isochoreshematics; P (\\ DisplayStyle P), V (\\ DisplayStyle V), T (\\ DisplayStyle T) - Pressure, specific volume and temperature of the medium; S (\\ DisplayStyle S) - Environment entropy.

For solutions and other complex physicochemical systems (for example, natural gas, oil), these expressions may produce a very greater error.

Solid body

If there are interface boundaries, elastic energy can be transmitted by surface waves of various types, whose speed differs from the speed of longitudinal and transverse waves. The energy of these oscillations can increase the energy of bulk waves many times.

Sacor. 23-11-2005 11:50

In principle, the question is not as simple as it seems, I found such a definition:

Sound speed, speed of propagation of any fixed phase of sound wave; Also called phase rate, unlike group velocity. S. s. Typically, the value is permanent for this substance at a given external conditions and does not depend on the frequency of the wave and its amplitude. In cases where this is not performed by S. s. Depends on the frequency, talk about the dispersion of sound.


So that is equal to the speed of sound in winter, in summer, in the fog, in the rain - these are such incomprehensible for me now things ...

Sergey13. 23-11-2005 12:20

with N.U. 320 m / s.

TL 23-11-2005 12:43

Than "denser" medium, the higher the rate of distribution of indignation (sound), in the air approx. 320-340m / c. (With height drops) 1300-1500 m / c in water (salted / fresh) 5000 m / s in metal, etc i., With the fog, the speed of sound will be higher, in the winter too higher, etc.

StartGamen. 23-11-2005 12:48

StartGamen. 23-11-2005 12:49

At the same time answered

Sacor. 23-11-2005 13:00

So the range of 320-340 m / s - looked at the reference book, there at 0 Celsius and pressure in 1 atmosphere the speed of sound in the air 331 m / s. So 340 in the frost, and 320 in the heat.
And now the most interesting thing, and what Togld the speed of bullets at subsonic ammunition?
Here for small-caliber cartridges for example with Ad.Ru such a classification:
Standard (subsonic) Cartridges speed up to 340 m / s
High Velocity cartridges (high-speed) speed from 350 to 400 m / s
Cartridges Hyper Velocity or Extra High Velocity (ultra-high-speed) Speed \u200b\u200bfrom 400 m / s and above
That is, Eley Tenex 331 m / s Sable 325 m / s are accumulated by subsonic, and the standard 341 m / s is no longer. Although those and these in principle lie in one range of sound velocities. Like this?

Kostya 23-11-2005 13:39

IMHO is not so bothering on it, you are not acoustics, but fond of shooting.

Sacor. 23-11-2005 13:42

qUOTE: Originally Posted by Kostya:
IMHO is not so bothering on it, you are not acoustics, but fond of shooting.

Yes, it's just interesting, and then all the doster is a sample, but how I turned out to be completely unqualified.

By the way, what is the speed of a dialing for silent shooting at x54, x39, 9pm?

John Jack 23-11-2005 13:43

The cartridges also have a scatter of the initial speed, and it depends on the temperature.

Greeng. 23-11-2005 14:15


Sound is an elastic longitudinal wave, the speed of the stem of which depends on the properties of the environment. Those. Above the terrain - below the air density - below speed. In contrast to the light - a transverse wave.
It is considered v \u003d 340 m / c (approximately).

But this is off

StartGamen. 23-11-2005 14:40




Current light has a transverse electromagnetic wave, and the sound mechanical longitudinal. If I understand their relatives of the current description of the same mathematical function.

But this is off

Hunt. 23-11-2005 14:48

That's what I wonder, the maximum atmospheric pressure was resting in the Urals (in general for a month) never rose to the parameters of the tubes. At this minute, there is 765 T-32. And what is interesting to the temperature below and the pressure below. Well ... This is how much I noted for myself, ... constant observations do not lead. I have a score. Tables were last year's pressure of 775mm \\ RT \\ art. Maybe the lack of oxygen in our edges is partially compensated by increased atmospheric pressure. Asked the question at home, it turns out that there is no data!. And these are people creating decompression tables for people like me! And for military runs (on a freezing) in our Palesties are prohibited, because Lack of oxygen. I think if the oxygen is disadvantaged, it means what is substituted, ... nitrogen, those and other density. And if you look at all this and count, you have to be a galactic class shooter. I am for myself (while the senor evokes over the calculator, and the customs over my parcels) decided: for 700 neither, whether the cartridges are flown.
I wrote and thought. After all, it was spoiled and stopped more than once, well, nafig all this. What to go to the Chepionate? Compete with whom?
... you read the forum and again carries. Bullets where to take, matrix, etc.
Conclusion: a terrible dependence on communicating with yourself similar people, loving weapons - homo ... (I propose to find a continuation of the expression)

Greeng. 23-11-2005 16:02

qUOTE: Originally posted by StartGamen:


I can IFF to develop - my diploma was called "nonlinear acoustoelectromagnetic interactions in crystals with quadratic electrodtroscia"

StartGamen. 23-11-2005 16:24

I have no physicist theoretical, so there were no sho "experiments". There was an attempt to take into account the second derivative and explain the emergence of resonance.
But the idea is correct


Khabarovsk 23-11-2005 16:34

Can I listen to the edge of the edge? I will not interfere, Chessloovo. Regards, Alexey

Antti. 23-11-2005 16:39

qUOTE: Originally posted by Greeng:


the main experimental method was apparently knocking a crystal magnet?

Square magnet on the crystal curve.

Sacor. 23-11-2005 19:03

Then another question, because of what winter sound sound seems loud than in the summer?

Svireppey 23-11-2005 19:27

I'll tell you all that's what.
Among the ammunition to the speed of the sound is close to.22LR. We put on the trunk of the moder (for removing the sound background) and fell onto the hundred, for example. And then, all the cartridges can be easily divided into dialing (you can hear how the target goes to the target - the light such "bunch" takes place) and on the superstructure - when hitting the target backs so that all the idea with the moder flies to the cat under the tail. From a donor I can note the pace, biathlon, from imported - RWS Target (well, I know them, and there is no choice of them in stores). From supersonic - for example, Lapua standard, cheap, interesting, but very noisy cartridges. Then we take the initial speeds from the manufacturer's website - and here you have an approximate range where the speed of sound is located at this temperature of the shoot.

StartGamen. 23-11-2005 19:56


Then another question, because of what winter sound sound seems loud than in the summer?

Winter mustache in the caps and therefore the rumor is dulled

Stasil0v 23-11-2005 20:25

And if seriously: with some kind of purpose, you need to know the real speed of sound for specific condition (in the sense of the practical point of view)? The goal usually determines the means and methods / accuracy of measurement. For me, it seems like to get to the target or on the hunt, it does not require ETU speed to know (if of course without a silencer) ...

Pashev 23-11-2005 20:38

In fact, the speed of sound is to some extent the limit for a stabilized bullet flight. If you look at the accelerated body, then the air resistance is growing to the sound barrier, it is rather sharply in front of the barrier, and then, on the passage of the barrier, it falls sharply (because the aviators sought to achieve supersonic). When braking, the picture is built in the reverse order. That is, when the speed ceases to be supersonic, the bullet is experiencing a sharp jump of the resistance of the air and can go a knuckle.

vyacheslav 23-11-2005 20:38




it turned out everything is completely unqualified.

The most interesting conclusion in the whole reasoning.

q123Q. 23-11-2005 20:44

And so, comrades, the speed of sound directly depends on the temperature, the greater the temperature, the greater the speed of the sound, and not exactly the opposite as noted at the beginning of the topic.
*************** /------- |
sound speed A \u003d \\ / K * R * T (this root is so indicated)

For air K \u003d 1.4 - This is an indicator of adiabat
R \u003d 287 - Specific gas constant for air
T - Temperature in Kelvin (0 degrees Celsius corresponds to 273.15 degrees Kelvin)
That is, at 0 Celsius A \u003d 331.3 m / s

Thus, in the range -20 +20 Celsius, the speed of sound changes in the ranges from 318.9 to 343.2 m / s

I think more questions will not arise.

As for what all this is necessary, this is necessary when studying flow regimes.

Sacor. 24-11-2005 10:32

Exhaustively, but from density, pressure does not depend on the sound?

BIT 24-11-2005 12:41

[B] If you look at the accelerated body, then the air resistance is growing up to the sound barrier, it is rather sharply before the barrier, and then, on the passage of the barrier, it drops sharply (because the aviators so sought to achieve supersonic).

I have already been pretty forgotten physics, but as far as I remember, the resistance of the air grows with increasing speed and to the "sound" and after. Only at the dialing, the main contribution makes overcoming the friction force of air, and at supersonic, this component decreases sharply, but increase energy losses to create a shock wave. A. In general, energy flows are increasing, and the farther, the more progressive.


Blackspring. 24-11-2005 13:52

I agree with Q123Q. As we were taught - the norm at 0 Celsius is 330 m / s, plus 1 degree - plus 1 m / s, minus 1 degree - minus 1 m / s. Completely working scheme for practical application.
Probably, the norm may vary from pressure, but the change will still be approximately a degree meter per second.
BS.

StartGamen. 24-11-2005 13:55

qUOTE: Originally Posted by Sacor:


Depends depends. But: there is such a law of the boil, according to which at a constant P / P1 \u003d const temperature, i.e. Changing the density is directly proportional to the change in pressure

Pashev 24-11-2005 14:13


Originally posted by Parashev:
[B]
I have already been pretty forgotten physics, but as far as I remember, the resistance of the air grows with increasing speed and to the "sound" and after. .

And I never knew never.

It grows to sound and after sound, and differently at different speeds, but it drops on the sound barrier. That is, 10 m / s to the sound speed resistance is higher than when 10 m / s after sound speed. Then grows again.
Of course, the nature of this resistance is different, so different objects in the form of a different barrier transition. Drop-like objects fly better to sound, after sound - with a sharp nose.


BIT 24-11-2005 14:54

Originally posted by Parashev:
[B]

That is, 10 m / s to the sound speed resistance is higher than when 10 m / s after sound speed. Then grows again.

Not certainly in that way. When moving a sound barrier, the total resistance force increases, and the jump, due to a sharp increase in energy consumption on the formation of a shock wave. The contribution of the friction force (or rather, the resistance force due to turbulence for the body) sharply decreases due to a sharp decrease in the density of the medium in the border layer and the body. Therefore, the optimal shape of the body at the dialing becomes non-optimal on the supersonic, and vice versa. A threatened telescope on a supertoum on supersonic creates a very powerful shock wave, and is experiencing much greater total resistance force, compared with the pointed but with the "blunting" rear (which practically does not matter on supersonic). With reverse transition, the rear, non-depended part creates a large, compared to the capacious body, turbulence and the trace of resistance. In general, the whole section of general physics is devoted to these processes - hydrodynamics, and it is easier to read the textbook. And the scheme set forth by you, as far as I can judge, does not correspond to reality.

Sincerely. BIT

Greeng. 24-11-2005 15:38

qUOTE: Originally posted by Parashev:


Drop-like objects fly better to sound, after sound - with a sharp nose.

URAAAA!
It remains to come up with a bullet who can fly to the nose forward to the top of the sound and w.pay after the barrier transition.

In the evening, Cognac in his bright head!

Machete. 24-11-2005 15:43

Inspired a discussion (off).

Gentlemen, did you drink cockroach?

BIT 24-11-2005 15:56

Recipe player, pliz.

Antti. 24-11-2005 16:47




In general, the whole section of general physics is dedicated to these processes - hydrodynamics ...

Hydra here and?


Pashev 24-11-2005 18:35




Hydra here and?

And the name is beautiful. Neither, of course, different processes in water and in the air, although there is also a common.

Here you can see what happens with the windshield coefficient on the sound barrier (3rd schedule):
http://kursy.rsuh.ru/aero/html/kurs_580_0.html

In any case - on the barrier there is a sharp change of the pattern of flowing, the perturbing motion of the bullet is to do this and may be useful to know the speed of sound.


Stasil0v 24-11-2005 20:05

Returning again into the practical plane, it turns out that in the transition to the dialing there are additional low-consumable "perturbations" leading to destabilization of bullets and an increase in scatter. It became for the achievement of sports purposes a supersonic smart cartridge in no case cannot be applied (and on the hunt the maximum possible accuracy does not prevent). What then the advantage of supersonic cartridges? More (non-imminent) energy and consequently slaughter power? And this is due to accuracy and noise more. Is it worth it at all supersonic 22ls to use?

gryud. 24-11-2005 21:42

qUOTE: Originally Posted by Hunt:
And for military runs (on a freezing) in our Palesties are prohibited, because Lack of oxygen. I think if the oxygen disadvantages, then the fact that is substituted, ... nitrogen,

It is impossible to talk about the replacement of KBLOROD azot because His replacement, just not. The percentage of atmospheric air is the same at any pressure. Another thing is that with a reduced pressure in the same inhaled air liter, the oxygen is actually less than under normal pressure, so the oxygen deficiency is developing. That is why pilots at altitudes above 3000m breathe through the masks of an air mixture to 40% oxygen.


q123Q. 24-11-2005 22:04

qUOTE: Originally Posted by Sacor:
Exhaustively, but from density, pressure does not depend on the sound?

Only through the temperature.

Pressure and density, or rather their ratio is rigidly related to the temperature
pressure / Density \u003d R * T
what is R, T, see in my post above.

That is, the speed of the sound is the unambiguous function of temperature.

Pashev 25-11-2005 03:03

It seems to me that the ratio of pressure and density is rigidly associated with the temperature only with adiabatic processes.
Are climatic changes in temperature and atmospheric pressure?

StartGamen. 25-11-2005 03:28

Correct question.
Answer: Climatic changes are not an adiabatic process.
But some kind of model you need to use ...

BIT 25-11-2005 09:55

qUOTE: Originally Posted by Antti:


Hydra here and?
Some, I suspect that in the air and water the picture can vary somewhat due to compressibility / incipiency. Or not?

We at the university was a joint course of hydro and aerodynamics as well as the Department of Hydrodynamics. Therefore, I called this section abbreviated. You are certainly right, the processes in liquids and gases can proceed in different ways, although there are a lot of common.


BIT 25-11-2005 09:59


What then the advantage of supersonic cartridges? More (non-imminent) energy and consequently slaughter power? And this is due to accuracy and noise more. Is it worth it at all supersonic 22ls to use?

StartGamen. 25-11-2005 12:44

The "accuracy" of the petty cartridge is due to the extremely weak heating of the trunk and a non-female lead bullet, and not the speed of its departure.

BIT 25-11-2005 15:05

About heating is clear. And non-boldness? Great making accuracy?

Stasil0v 25-11-2005 20:48

qUOTE: Originally posted by Bit:


IMHO - Ballistics, tobish trajectory. Less flowing time - less external perturbations. But in general, the question arises: because when moving to the dialing, the resistance of the air is sharply reduced, then it should sharply decrease and overturning momentum, and then increase the stability of the bullet? Is it because the petty chuck is one of the most accurate?

Machete. 26-11-2005 02:31

qUOTE: Originally posted by stasil0v:


Opinions were divided. In your opinion, a supersonic bullet comes out when moving to a doster stabilizes. And on the passage, on the contrary, it arises an additional perturbing effect is a worsening stabilization.

Dr. Watson. 26-11-2005 12:11

Exactly.

BIT 28-11-2005 12:37

And did not think to argue. Just asked questions and, opening his mouth, I did not listen.

Sacor. 28-11-2005 14:45

qUOTE: Originally posted by Machete:


In this case, Pashev is absolutely right - with reverse transvance transition, the bullet is destabilized. That is why the maximum shooting range for each particular cartridge in Longreeignge is determined by the remote transvance transition distance.

It turns out that a small-caliber bullet released at a speed of 350 m / s somewhere on 20-30 m is very destabilized? And accuracy deteriorates significantly.

Length and distance Mass Measures of bulk products and food Square Volume and units of measurement in culinary recipes Temperature Pressure, Mechanical voltage, Jung Module Energy and operation Power Power Time Linear speed Flat Angle Thermal efficiency and fuel efficiency Number of units of measurement number of information Currency Courses Sizes Women's clothing and shoes sizes of men's clothing and shoes angular speed and speed speed acceleration angular acceleration density specific volume of inertia torque torque torque specific heat combustion (by weight) energy density and specific heat combustion (by volume) temperature difference thermal expansion thermal temperature Resistance Specific thermal conductivity Specific heat Energetic exposure, thermal radiation power The heat flux density The heat transfer coefficient volumetric consumption mass flow rate molar consumption density of the mass flux molar concentration of mass Ontination in solution dynamic (absolute) viscosity kinematic viscosity surface tension vapor permeability vapor permeability, steam transfer speed Sound level sensitivity of microphones Sound pressure level (SPL) Brightness light light Light resolution in computer graphics frequency and wavelength optical power in diopters and focal length optical power in diopters and focal length Dioptia and an increase in lenses (×) Electric charge linear density charge surface density charge volumetric density charge electric current linear current density Surface density current electric field electric fields Electrostatic potential and voltage Electrical resistance Specific electrical resistance Electrical conductivity Specific electrical conductivity Electrical capacity Inductivity American Caliber Wires in DBM (dBm or dBmW), DBV (DBV), watts, etc. Units Magnethodific power magnetic field tension Magnetic sweat OK magnetic induction Power absorbed dose of ionizing radiation radioactivity. Radioactive decay radiation. Exposure dose radiation. Absorbed dose decimal consoles Data transmission typography and image processing Unit of measurement of timber volume Calculation of molar mass Periodic system of chemical elements D. I. Mendeleev

1 kilometer per hour [km / h] \u003d 0.0001873459079907 Speed \u200b\u200bspeed in fresh water

Source value

Transformed value

meter per second meter per hour per minute kilometer per hour kilometer per minute kilometer per second centimeter per hour centimeter per minute centimeter per second millimeter per minute millimeter per minute millimeter per second per hour foot per minute ft per second yard per hour yard A minute yard per second mile per hour per minute miles per second knot knot (Brit.) Speed \u200b\u200blight in vacuum First cosmic velocity Second cosmic speed Third space speed Earth speed Speed \u200b\u200bspeed in fresh water Sound speed in seawater (20 ° C, Depth 10 meters) Maha number (20 ° C, 1 atm) MAKH Number (SI standard)

American Caliber Wiring

Read more about speed

General

Speed \u200b\u200bis a measure of the distance traveled during a certain time. The speed can be scalar value and vector - while the direction of movement is taken into account. The speed of movement in a straight line is called linear, and around the circle - angular.

Speed \u200b\u200bmeasurement

Middle speed v. Find, sharing the total distance passed Δ x. For the total time Δ t.: v. = ∆x./∆t..

In the system, the speed is measured in meters per second. Kilometers per hour in the metric system and miles per hour in the United States and the UK are also widely used. When the direction is also indicated, for example 10 meters per second north, then we are talking about vector velocity.

The speed of moving with the acceleration of bodies can be found with the help of formulas:

• a.with initial speed u. during the period Δ t.has the final speed v. = u. + a.×∆ t..
• Body moving with constant acceleration a.with initial speed u. and the final speed v., has an average velocity Δ v. = (u. + v.)/2.

Average speed

Speed \u200b\u200bof light and sound

According to the theory of relativity, the speed of light in vacuum is the greatest speed with which energy and information can move. It is denoted by Constanta c. and equal c. \u003d 299 792 458 meters per second. Matter cannot move at the speed of light, because for this it will take an infinite amount of energy, which is impossible.

Sound speed is usually measured in an elastic medium, and is 343.2 meters per second in dry air at 20 ° C. The speed of sound is the lowest in the gases, and the highest - in solids. It depends on density, elasticity, and the substance shift module (which shows the degree of deformation of the substance during the shear load). Mach number M. - This is the ratio of body velocity in a fluid or gas environment to sound speed in this environment. It can be calculated by the formula:

M. = v./a.,

where a. - this is the speed of sound in the medium, and v. - body speed. Machum is usually used in determining speeds close to sound speed, such as aircraft speeds. This value is non-permanent; It depends on the state of the medium, which, in turn, depends on pressure and temperature. Supervice speed - speed exceeding 1 max.

Vehicle speed

Below are some vehicle speeds.

• Passenger aircraft with turboclerous engines: the cruising speed of passenger aircraft - from 244 to 257 meters per second, which corresponds to 878-926 kilometers per hour or m \u003d 0.83-0.87.
• High-speed trains (like Sinkansen in Japan): Such trains reaches maximum speeds from 36 to 122 meters per second, that is, from 130 to 440 kilometers per hour.

Speed \u200b\u200bof animals

The maximum speed of some animals is approximately equal:



Speed \u200b\u200bman

• People walk at a speed of approximately 1.4 meters per second or 5 kilometers per hour, and run at speeds of about 8.3 meters per second, or up to 30 kilometers per hour.

Examples of different speeds

Four-dimensional speed

In classical mechanics, vector speed is measured in three-dimensional space. According to the special theory of relativity, the space is four-dimensional, and the fourth dimension is also taken into account in measuring speed - space-time. Such speed is called four-dimensional speed. Its direction may vary, but the value is constant and equal c., that is, the speed of light. Four-dimensional speed is defined as

U \u003d ∂x / ∂τ

where x. Represents the world line - a curve in space-time, according to which the body moves, and τ - "own time", equal to the interval along the global line.

Group speed

Group velocity is the speed of propagation of waves, which describes the speed of the propagation of the wave group and determining the rate of transmission energy of the waves. It can be calculated as ∂ ω /∂k.where k. - wave number, and ω - angular frequency. K. Measure in radians / meter, and the scalar frequency of fluctuations of waves ω - in radians per second.

Hyperzvukoy speed

Hyperzvukovka speed is a speed that exceeds 3000 meters per second, that is, many times higher than the speed of sound. Solid bodies moving at such a speed acquire the properties of liquids, since due to inertia, the load in this state is stronger than the forces while holding together the molecules of the substance during collision with other bodies. Under ultrahigh hypersonic speeds, two colliding solids are converted to gas. In the body of the body, they move at such a speed, and engineers designing space ships, orbital stations and spaces, should take into account the possibility of a collision of a station or cosmonaut with space trash and other objects when working in open space. With such a collision, the lifting of the spacecraft and the spacecraft suffers. Equipment developers carry out experiments of collisions on hypersonic speed in special laboratories to determine how strong collisions are withstanding the spacecraft, as well as the skin and other parts of the spacecraft, such as fuel tanks and solar panels, checking them for strength. For this, the space and trim are exposed to blows with different objects from a special installation with supersonic speeds exceeding 7,500 meters per second.

The first attempts to understand the nature of the occurrence of sound were made more than two thousand years ago. In the works of the ancient Greek scientists, Ptolemy and Aristotle are made true assumptions that the sound is generated by fluctuations in the body. Moreover, Aristotle argued that the speed of sound is measurable and the ultimate magnitude. Of course, in ancient Greece there were no technical capabilities for any accurate measurements, so the speed of sound was relatively accurately measured only in the seventeenth century. To do this, the comparison method was used between the outbreak detection time from the shot and time, through which the sound did the observer. As a result of numerous experiments, scientists concluded that the sound extends to the air at a speed of 350 to 400 meters per second.

The researchers also found out that the value of the speed of propagation of sound waves in a particular medium directly depends on the density and temperature of this medium. So, the air is rarellied, the slower the sound moves along it. In addition, the speed of sound is higher than the higher the temperature of the medium. To date, it is believed that the speed of propagation of sound waves in the air under normal conditions (at the sea level at 0 ° C) is 331 meters per second.

Mach number

In real life, the speed of sound is a significant parameter in aviation, however, at those heights, where usually, the environmental characteristics are very different from normal. That is why the aviation uses a universal concept, which is called the number of Mach, named after the Austrian Ernst Mach. This number is the velocity of the object to be divided into local sound speed. It is obvious that the smaller the sound speed in the medium with specific parameters, the greater the number of Mach, even if the speed of the object itself does not change.

The practical application of this number is due to the fact that the movement at speed, which is higher than the speed of sound, is significantly different from moving at subsonic speeds. Basically, this is due to the change in the aerodynamics of the aircraft, the deterioration of its controllability, the heating of the body, as well as with the resistance of the waves. These effects are observed only when the number of maha exceeds one, that is, the object overcomes the sound barrier. At the moment, there are formulas that allow you to calculate the speed of sound with certain parameters of the air, and, therefore, calculate the number of maha for different conditions.

A high speed is the speed of light in vacuo, that is, the space free from the substance. The scientist community was taken by its value 299 792 458 m / s (or 1,079,252,848.8 km / h). At the same time, the most accurate measurement of the speed of light based on the reference meter, carried out in 1975, showed that it is 299,792,458 ± 1.2 m / s. With the speed of light, both the visible light and other types of electromagnetic radiation are distributed, for example, radio waves, X-rays, gamma quanta.

The speed of light in vacuum is a fundamental physical constant, i.e. its value does not depend on any external parameters and does not change with time. This speed does not depend on the movement of the source of the waves, nor from the observer reference system.

What is the speed of sound?

The speed of sound differs depending on the medium in which the elastic waves apply. It is impossible to calculate the speed of sound in vacuo, since the sound in such conditions cannot be distributed: there is no elastic medium in vacuo, and the elastic mechanical oscillations may not occur. As a rule, slower sound propagates in gas, a little faster - in the liquid, most quickly - in solid bodies.

So, according to the physical encyclopedia edited by Prokhorov, the speed of sound in some gases at 0 ° C and normal pressure (101325 Pa) is (m / c):

Sound speed in some liquids at 20 ° C is equal to (m / c):

In a solid medium, longitudinal and transverse elastic waves apply, and the speed of longitudinal is always larger than transverse. Sound speed in some solid bodies is (m / c):

Today, many new buildings, equipping an apartment, are forced to carry out additional work, including the soundproofing of their home, because Applied standard materials allow only partly to hide what is happening in their own home, and not be interested in against the will with the communication of the neighbors.

On in solids there is at least the density and elasticity of a substance opposing the wave. Therefore, when the facilities of the premises layer adjacent to the bearing wall make it soundproofing with "intake" from above and below. It reduces in decibels sometimes more than 10 times. Then the basalt mats are placed, and from above - plasterboard sheets that reflect the sound outside of the apartment. When the sound wave "flies" to such a design, it fades in the layers of the insulator, which are porous and soft. If the sound is of great strength, then the materials, absorbing it, may even heat up.

The elastic substances, such as water, wood, metals, are well transmitted so we hear the beautiful "singing" of musical instruments. And some nations in the past determined the approach, for example, riders, applying the ear to the ground, which is also quite elastic.

The speed of sound in km depends on the characteristics of the environment in which it distributes. In particular, its pressure, chemical composition, temperature, elasticity, density and other parameters may affect the process. For example, in a steel sheet, the sound wave passes at a speed of 5100 meters per second, in glass - about 5000 m / s, in the tree and granite - about 4000 m / s. To transfer speed to kilometers per hour you need to multiply indicators on 3600 (seconds in an hour) and divided by 1000 (meters in a kilometer).

The speed of sound in km in the aqueous medium is different for substances with different salinity. For fresh water at a temperature of 10 degrees Celsius, it is about 1450 m / s, and at a temperature of 20 degrees Celsius and the same pressure - already about 1490 m / s.

Salted medium is distinguished by an obviously greater speed of sounding oscillations.

The propagation of sound in the air also depends on temperature. When this parameter is valid, equal to 20, sound waves pass at a speed of about 340 m / s, which is about 1200 km / h. And at zero degrees, the speed slows down to 332 m / s. Returning to our apartment insulators, we can find out that in such a material, as a plug, which is often used to reduce the level of external noise, the speed of sound in the CM is only 1,800 km / h (500 meters per second). This is ten times lower than this characteristic in steel details.

The sound wave is a longitudinal medium fluctuate in which it spreads. When passing, for example, the melodies of the musical work through some obstacle, the level of its volume decreases, because It changes the frequency remains the same, thanks to which we hear the female voice as a female, and the male is like a male. The most interesting is the place where the speed of sound is close to zero. This is a vacuum in which the waves of this type almost do not apply. To demonstrate how it works, physicists put the ringing alarm clock under the hood from which the air is screwed down. The more air affection, the quieter hears the call.