The first attempts to understand the origin of sound were made more than two thousand years ago. In the writings of the ancient Greek scientists Ptolemy and Aristotle, correct assumptions are made that sound is generated by vibrations of the body. Moreover, Aristotle argued that the speed of sound is measurable and finite. Of course, in Ancient Greece did not have technical capabilities for any precise measurements, so the speed of sound was measured relatively accurately only in the seventeenth century. For this, a comparison method was used between the detection time of a flash from a shot and the time after which the sound reached the observer. As a result of numerous experiments, scientists came to the conclusion that sound propagates in the air at a speed of 350 to 400 meters per second.

The researchers also found 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 rarer the air, the slower sound travels through it. In addition, the speed of sound is the higher, the higher the temperature of the medium. To date, it is generally accepted that the speed of propagation of sound waves in the air under normal conditions (at sea level at a temperature of 0ºС) is 331 meters per second.

Mach number

IN real life the speed of sound is a significant parameter in aviation, however, at those altitudes, where usually , the characteristics environment very different from normal. That is why aviation is used universal concept, which is called the Mach number, named after the Austrian Ernst Mach. This number is the speed of the object divided by the local speed of sound. Obviously, the lower the speed of sound in a medium with specific parameters, the greater the Mach number will be, even if the speed of the object itself does not change.

Practical use This number is due to the fact that movement at a speed that is higher than the speed of sound differs significantly from movement at subsonic speeds. Basically, this is due to a change in the aerodynamics of the aircraft, deterioration of its controllability, heating of the hull, as well as wave resistance. These effects are observed only when the Mach number 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 for certain air parameters, and, therefore, calculate the Mach number for different conditions.

Sound speed- speed of propagation of elastic waves in a medium: both longitudinal (in gases, liquids or solids) and transverse, shear (in solids). It is determined by the elasticity and density of the medium: as a rule, the speed of sound in gases is less than in liquids, and in liquids it is less than in solids. Also, in gases, the speed of sound depends on the temperature of the given substance, in single crystals - on the direction of wave propagation. Usually does not depend on the frequency of the wave and its amplitude; in cases where the speed of sound depends on frequency, one speaks of the dispersion of sound.

Encyclopedic YouTube

Already among ancient authors there is an indication that the sound is due to the oscillatory movement of the body (Ptolemy, Euclid). Aristotle notes that the speed of sound has a finite value and correctly imagines the nature of sound. Attempts experimental definition sound speeds date back to the first half of the 17th century. F. Bacon in the "New Organon" pointed out the possibility of determining the speed of sound by comparing the time intervals between a flash of light and the sound of a shot. Using this method, various researchers (M. Mersenne, P. Gassendi, W. Derham, a group of scientists from the Paris Academy of Sciences - D. Cassini, Picard, Huygens, Römer) determined the value of the speed of sound (depending on the experimental conditions, 350-390 m /With). Theoretically, the question of the speed of sound was first considered by Newton in his Principia. Newton actually assumed the isothermal propagation of sound, so he received an underestimate. Correct theoretical value the speed of sound was obtained by Laplace. [ ]

Calculation of velocity in liquid and gas

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

c = 1 β ρ (\displaystyle c=(\sqrt (\frac (1)(\beta \rho ))))

In partial derivatives:

c = − v 2 (∂ p ∂ v) s = − v 2 C p C v (∂ p ∂ v) T (\displaystyle c=(\sqrt (-v^(2)\left((\frac (\ partial p)(\partial v))\right)_(s)))=(\sqrt (-v^(2)(\frac (Cp)(Cv))\left((\frac (\partial p) (\partial v))\right)_(T))))

where β (\displaystyle \beta ) is the adiabatic compressibility of the medium; ρ (\displaystyle \rho ) - density; C p (\displaystyle Cp) - isobaric heat capacity; C v (\displaystyle Cv) - isochoric heat capacity; p (\displaystyle p) , v (\displaystyle v) , T (\displaystyle T) - pressure, specific volume and temperature of the medium; s (\displaystyle s) - entropy of the environment.

For solutions and other complex physico-chemical systems (for example, natural gas, oil) these expressions can give a very large error.

Solids

In the presence of interfaces, elastic energy can be transferred through surface waves of various types, the speed of which differs from the speed of longitudinal and transverse waves. The energy of these oscillations can be many times greater than the energy of bulk waves.

Sacor 23-11-2005 11:50

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

The speed of sound, the speed of propagation of any fixed phase of a sound wave; also called the phase velocity, in contrast to the group velocity. S. h. usually the value is constant for a given substance under given external conditions and does not depend on the frequency of the wave and its amplitude. In cases where this is not done and S. z. depends on the frequency, they talk about the dispersion of sound.


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

Sergey13 23-11-2005 12:20

at n.o. 320 m/s.

TL 23-11-2005 12:43

The "dense" the medium, the higher the propagation speed of the perturbation (sound), in the air approx. 320-340m/s (falls with height) 1300-1500 m/s in water (salt/fresh) 5000 m/s in metal etc

StartGameN 23-11-2005 12:48

StartGameN 23-11-2005 12:49

Answered at the same time

Sacor 23-11-2005 13:00

So the range is 320-340 m / s - I looked at the reference book, there at 0 Celsius and a pressure of 1 atmosphere, the speed of sound in air is 331 m / s. So 340 in the cold, and 320 in the heat.
And now the most interesting thing, but what then is the bullet speed of subsonic ammunition?
Here is a classification for small-caliber cartridges, for example from ada.ru:
Standard (subsonic) cartridges speed up to 340 m/s
Cartridges High velocity (high-speed) speed from 350 to 400 m/s
Cartridges Hyper Velocity or Extra high velocity (ultra-high speed) speed from 400 m/s and above
That is, Eley Tenex 331 m / s Sable 325 m / s are considered subsonic, and Standard 341 m / s is no longer. Although both those and these, in principle, lie in the same range of sound speeds. Like this?

Kostya 23-11-2005 13:39

IMHO you shouldn't bother with it so much, you're not into acoustics, but you are fond of shooting.

Sacor 23-11-2005 13:42

quote: Originally posted by Kostya:
IMHO you shouldn't bother with it so much, you're not into acoustics, but you are fond of shooting.

Yes, it’s just interesting, otherwise everything is supersonic subsonic, but as I dug, everything turned out to be completely ambiguous.

By the way, what is the subsonic speed for silent shooting at x54, x39, 9PM?

John Jack 23-11-2005 13:43

The cartridges also have a spread in the initial speed, and it also depends on the temperature.

GreenG 23-11-2005 14:15


Sound is an elastic longitudinal wave, the propagation speed of which depends on the properties of the environment. Those. higher terrain - lower air density - lower speed. Unlike light - a transverse wave.
It is generally accepted that V = 340 m / s (approximately).

However, this is off

StartGameN 23-11-2005 14:40




Current light has a transverse electromagnetic wave, and sound has a mechanical longitudinal wave. If I understand them correctly, the description of the same mathematical function makes them related.

However, this is off

Hunt 23-11-2005 14:48

That's what I'm wondering, resting in the Urals, the maximum atmospheric pressure (for a month as a whole) never rose to the local parameters. At the moment there are 765 t-32s. And interestingly, the temperature is lower and the pressure is lower. Well ... as far as I noted for myself, ... I don’t conduct constant observations. I also have a score. the tables were last year's for a pressure of 775 mm \ rt \ st. Maybe the lack of oxygen in our area is partially offset by increased atmospheric pressure. I asked a question at my department, it turns out there is NO DATA !. And these are people who create decompression tables for people like me! And for the military, jogging (on physical exercises) is prohibited in our Palestinians, because. lack of oxygen. I think if there is a lack of oxygen, it means that it is replaced by ... nitrogen, that is, the density is different. And if you look at all this and count, you have to be a galactic-class shooter. I decided for myself (while the Senior is working on the calculator, and the customs on my parcels) I decided: For 700 no, no, it’s okay to shoot cartridges.
I wrote and thought. After all, he spat and swore more than once, well, what for all this. What to go to the championship? Compete with whom?
... You read the forum and again bears. Where to get bullets, matrices, etc.
CONCLUSION: Terrible addiction to communication with yourself like 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 develop off - my diploma was called "Nonlinear acoustic electromagnetic interactions in crystals with quadratic electrostriction"

StartGameN 23-11-2005 16:24

I am not a theoretical physicist, so there were no "experiments". There was an attempt to take into account the second derivative and explain the occurrence of resonance.
But the idea is right


Khabarovsk 23-11-2005 16:34

Can I stand here on the edge and listen? I won't interfere, honestly. Regards, Alexey

Antti 23-11-2005 16:39

quote: Originally posted by GreenG:


basic experimental method was, apparently, knocking a magnet on a crystal?

Square magnet on a crooked crystal.

Sacor 23-11-2005 19:03

Then another question, because of what in winter the sound of a shot seems louder than in summer?

SVIREPPEY 23-11-2005 19:27

I'll tell you all this.
From ammunition, the speed of sound is close to .22lr. We put a moder on the barrel (to remove the sound background) and fire on a hundred, for example. And then all the cartridges can be easily divided into subsonic (you can hear how it flies into the target - such a light "bunch" takes place) and into supersonic - when it hits the target, it bangs so that the whole idea with the moderator flies down the drain. From subsonic, I can note tempo, biathlon, from imported ones - RWS Target (well, I don’t know much about them, and the choice in stores is not the right one). 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's the approximate range where the speed of sound is located at a given shooting temperature.

StartGameN 23-11-2005 19:56


Then another question, because of what in winter the sound of a shot seems louder than in summer?

In winter, everyone wears hats, and therefore hearing is dulled.

STASIL0V 23-11-2005 20:25

But seriously: for what purpose is it required to know the real speed of sound for specific conditions (in the sense from a practical point of view)? the purpose usually determines the means and methods/accuracy of the measurement. For me, it seems like to hit a target or on a hunt you don’t need to know this speed (unless, of course, without a silencer) ...

Parshev 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 up to the sound barrier, air resistance increases, in front of the barrier quite sharply, and then, after passing through the barrier, it drops sharply (because the aviators were so eager to achieve supersonic speed). When braking, the picture is built in the reverse order. That is, when the speed ceases to be supersonic, the bullet experiences a sharp jump in air resistance and can go somersault.

vyacheslav 23-11-2005 20:38




everything turned out to be quite ambiguous.

The most interesting conclusion in the whole argument.

q123q 23-11-2005 20:44

And so, comrades, the speed of sound directly depends on the temperature, the higher the temperature, the greater the speed of sound, and not at all the other way around, as noted at the beginning of the topic.
*************** /------- |
speed of sound a=\/ k*R*T (this is the root so designated)

For air, k = 1.4 is the adiabatic exponent
R = 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 = 331.3 m / s

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

I don't think there will be any more questions.

As for what all this is for, it is necessary in the study of flow regimes.

Sacor 24-11-2005 10:32

Exhaustive, but doesn't the speed of sound depend on density, pressure?

BIT 24-11-2005 12:41

[B] If you look at the accelerated body, then up to the sound barrier the air resistance increases, before the barrier it is quite sharp, and then, after passing through the barrier, it drops sharply (that's why the aviators were so eager to achieve supersonic).

I already pretty much forgot physics, but as far as I remember, air resistance increases with increasing speed, both before the "sound" and after. Only at subsonic the main contribution is made by overcoming the force of friction against the air, and at supersonic this component sharply decreases, but the energy losses for the creation of a shock wave increase. A. in general, energy losses increase, and the further, the more progressive.


blackspring 24-11-2005 13:52

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. Quite a working scheme for practical use.
Probably, the norm can change with pressure, but the change will still be about a degree meter per second.
BS

StartGameN 24-11-2005 13:55

quote: Originally posted by Sacor:


Depends, depends. But: there is such a Boyle's law, according to which at a constant temperature p/p1=const, i.e. change in density is directly proportional to change in pressure

Parshev 24-11-2005 14:13


Originally posted by Parshev:
[B]
I already pretty much forgot physics, but as far as I remember, air resistance increases with increasing speed, both before the "sound" and after. .

And I never knew.

It grows both before sound and after sound, and in different ways at different speeds, but falls at the sound barrier. That is, 10 m/s before the speed of sound, the resistance is higher than when it is 10 m/s after the speed of sound. Then it grows again.
Of course, the nature of this resistance is different, so objects of different shapes cross the barrier in different ways. Drop-shaped objects fly better before the sound, after the sound - with a sharp nose.


BIT 24-11-2005 14:54

Originally posted by Parshev:
[B]

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

Not certainly in that way. When crossing the sound barrier, the TOTAL resistance force increases, moreover, abruptly, due to a sharp increase in energy consumption for the formation of a shock wave. The contribution of the FRICTION FORCE (more precisely, the drag force due to turbulence behind the body) sharply decreases due to a sharp decrease in the density of the medium in the boundary layer and behind the body. Therefore, the optimal shape of the body at subsonic becomes suboptimal at supersonic, and vice versa. A drop-shaped body streamlined at subsonic creates a very powerful shock wave at supersonic, and experiences a much greater TOTAL resistance force, compared to a pointed but with a "blunt" rear part (which practically does not matter at supersonic). During the reverse transition, the rear non-streamlined part creates more turbulence compared to the drop-shaped body and, consequently, a drag force. In general, a whole section of general physics is devoted to these processes - hydrodynamics, and it is easier to read a textbook. And as far as I can judge, the scheme you outlined is not true.

Sincerely. BIT

GreenG 24-11-2005 15:38

quote: Originally posted by Parshev:


Drop-shaped objects fly better before the sound, after the sound - with a sharp nose.

Hooray!
It remains to come up with a bullet that can fly nose first at super sound and well .. sing after crossing the barrier.

In the evening I'll sip cognac for my bright head!

Machete 24-11-2005 15:43

Inspired by discussion (off).

Gentlemen, have you been drinking cockroach?

BIT 24-11-2005 15:56

Recipe, please.

Antti 24-11-2005 16:47




In general, a whole section of general physics is devoted to these processes - hydrodynamics ...

What's with the hydra?


Parshev 24-11-2005 18:35




What's with the hydra?

And the name is beautiful. It has nothing to do with, of course, different processes in water and in air, although there is something in common.

Here you can see what happens to the drag coefficient at the sound barrier (3rd graph):
http://kursy.rsuh.ru/aero/html/kurs_580_0.html

In any case - there is a sharp change in the flow pattern on the barrier, perturbing the movement of the bullet - for this it may be useful to know the speed of sound.


STASIL0V 24-11-2005 20:05

Returning again to the practical plane, it turns out that when switching to subsonic, additional unpredictable "perturbations" arise, leading to destabilization of the bullet and an increase in dispersion. Therefore, in order to achieve sporting goals, a supersonic small-sized cartridge should in no case be used (and the maximum possible accuracy will not hurt when hunting). What then is the advantage of supersonic cartridges? More (not much) energy and therefore lethal force? And this is due to accuracy and more noise. Is it worth using a supersonic 22lr at all?

gyrud 24-11-2005 21:42

quote: Originally posted by Hunt:
And for the military, jogging (on physical exercises) is prohibited in our Palestinians, because. lack of oxygen. I think if there is a lack of oxygen, then what is replaced, ... with nitrogen,

It is impossible to talk about any substitution of kb oxygen by nitrogen, because there is simply no substitute for it. Percentage composition atmospheric air the same at any pressure. Another thing is that at reduced pressure in the same liter of inhaled air, there is actually less oxygen than at normal pressure, and oxygen deficiency develops. That is why pilots at altitudes above 3000m breathe through masks with an air mixture enriched with up to 40% oxygen.


q123q 24-11-2005 22:04

quote: Originally posted by Sacor:
Exhaustive, but doesn't the speed of sound depend on density, pressure?

Only through temperature.

Pressure and density, or rather their ratio, is strictly related to temperature.
pressure/density = R*T
what is R, T see in my post above.

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

Parshev 25-11-2005 03:03

It seems to me that the ratio of pressure and density is strictly related to temperature only in adiabatic processes.
Are climate changes in temperature and atmospheric pressure such?

StartGameN 25-11-2005 03:28

Correct question.
Answer: Climate change is not an adiabatic process.
But you need to use some kind of model ...

BIT 25-11-2005 09:55

quote: Originally posted by Antti:


What's with the hydra?
Somehow, I suspect that in air and water the picture may differ somewhat due to compressibility / incompressibility. Or not?

We had a combined course in hydro- and aerodynamics at the university, as well as a department of hydrodynamics. That's why I've abbreviated this section. Of course, you are right, processes in liquids and gases can proceed in different ways, although there is a lot in common.


BIT 25-11-2005 09:59


What then is the advantage of supersonic cartridges? More (not much) energy and therefore lethal force? And this is due to accuracy and more noise. Is it worth using a supersonic 22lr at all?

StartGameN 25-11-2005 12:44

The "accuracy" of a small-sized cartridge is due to the extremely weak heating of the barrel and a non-jacketed lead bullet, and not to the speed of its departure.

BIT 25-11-2005 15:05

I understand about heating. And the innocence? Greater manufacturing precision?

STASIL0V 25-11-2005 20:48

quote: Originally posted by BIT:


IMHO - ballistics, tobish trajectory. Less flying time - less external disturbances. In general, the question arises: Since when switching to subsonic air resistance sharply decreases, should the overturning moment also decrease sharply, and consequently increase the stability of the bullet? Is that why a small cartridge 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 switching to subsonic, it stabilizes. And according to Parshev, on the contrary, an additional perturbing effect arises that worsens stabilization.

Dr. Watson 26-11-2005 12:11

Exactly.

BIT 28-11-2005 12:37

And I didn't think to argue. He simply asked questions and, opening his mouth, listened.

Sacor 28-11-2005 14:45

quote: Originally posted by Machete:


In this case, Parshev is absolutely right - during the reverse transonic transition, the bullet destabilizes. That is why the maximum firing range for each specific cartridge in LongRange is determined by the distance of the reverse transonic transition.

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

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1 kilometer per hour [km/h] = 0.0001873459079907 speed of sound in fresh water

Initial value

Converted value

meter per second meter per hour meter per minute kilometer per hour kilometer per minute kilometers per second centimeter per hour centimeter per minute centimeter per second millimeter per hour millimeter per minute millimeter per second foot per hour foot per minute foot per second yard per hour yard per minute yard per second mile per hour mile per minute mile per second knot knot (Brit.) speed of light in vacuum first space velocity second space velocity third space velocity earth's rotation speed sound speed in fresh water sound speed in sea water (20°C, depth 10 meters) Mach number (20°C, 1 atm) Mach number (SI standard)

American wire gauge

More about speed

General information

Speed ​​is a measure of the distance traveled in a given time. Velocity can be a scalar quantity or a vector value - the direction of motion is taken into account. The speed of movement in a straight line is called linear, and in a circle - angular.

Speed ​​measurement

average speed v find by dividing the total distance traveled ∆ x on total time ∆t: v = ∆x/∆t.

In the SI system, speed is measured in meters per second. Also commonly used are kilometers per hour in the metric system and miles per hour in the US and UK. When, in addition to the magnitude, the direction is also indicated, for example, 10 meters per second to the north, then we are talking about vector speed.

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

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

Average speeds

The speed of light and sound

According to the theory of relativity, the speed of light in a vacuum is the highest speed at which energy and information can travel. It is denoted by the constant c and equal to c= 299,792,458 meters per second. Matter cannot move at the speed of light because it would require an infinite amount of energy, which is impossible.

The speed of sound 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 lowest in gases and highest in solids. It depends on the density, elasticity, and shear modulus of the substance (which indicates the degree of deformation of the substance under shear loading). Mach number M is the ratio of the speed of a body in a liquid or gas medium to the speed of sound in this medium. It can be calculated using the formula:

M = v/a,

Where a is the speed of sound in the medium, and v is the speed of the body. The Mach number is commonly used in determining speeds close to the speed of sound, such as aircraft speeds. This value is not constant; it depends on the state of the medium, which, in turn, depends on pressure and temperature. Supersonic speed - speed exceeding 1 Mach.

Vehicle speed

Below are some vehicle speeds.

• Passenger aircraft with turbofan engines: the cruising speed of passenger aircraft is from 244 to 257 meters per second, which corresponds to 878–926 kilometers per hour or M = 0.83–0.87.
• High-speed trains (like the Shinkansen in Japan): These trains reach top speeds of 36 to 122 meters per second, i.e. 130 to 440 kilometers per hour.

animal speed

The maximum speeds of some animals are approximately equal:



human speed

• Humans walk at about 1.4 meters per second, or 5 kilometers per hour, and run at up to about 8.3 meters per second, or 30 kilometers per hour.

Examples of different speeds

four dimensional speed

In classical mechanics, the vector velocity is measured in three-dimensional space. According to special theory relativity, space is four-dimensional, and the fourth dimension, space-time, is also taken into account in the measurement of speed. This speed is called four-dimensional speed. Its direction may change, but the magnitude is constant and equal to c, which is the speed of light. Four-dimensional speed is defined as

U = ∂x/∂τ,

Where x represents the world line - a curve in space-time along which the body moves, and τ - "proper time", equal to the interval along the world line.

group speed

Group velocity is the velocity of wave propagation, which describes the propagation velocity of a group of waves and determines the rate of wave energy transfer. It can be calculated as ∂ ω /∂k, Where k is the wave number, and ω - angular frequency . K measured in radians / meter, and the scalar frequency of wave oscillations ω - in radians per second.

Hypersonic speed

Hypersonic speed is a speed exceeding 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 loads in this state are stronger than the forces that hold the molecules of matter together during a collision with other bodies. At ultra-high hypersonic speeds, two colliding solid bodies turn into gas. In space, bodies move exactly at this speed, and engineers designing spacecraft, orbital stations, and spacesuits must take into account the possibility of a station or astronaut colliding with space debris and other objects when working in outer space. In such a collision, the skin of the spacecraft and the suit suffer. Equipment designers conduct hypersonic collision experiments in special laboratories to determine how strong impact suits, as well as skins and other parts, can withstand. spaceship, such as fuel tanks and solar panels, testing them for strength. To do this, spacesuits and skin are subjected to impacts by various objects from a special installation with supersonic speeds exceeding 7500 meters per second.

The highest speed is considered to be the speed of light in a vacuum, i.e. a space free of matter. The scientific community accepted its value as 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 a reference meter, carried out in 1975, showed that it is 299,792,458 ± 1.2 m / s. At the speed of light, both visible light and other forms of light travel. electromagnetic radiation such as 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 motion of the wave source, nor on the reference frame of the observer.

What is the speed of sound?

The speed of sound differs depending on the medium in which elastic waves propagate. It is impossible to calculate the speed of sound in vacuum, since sound cannot propagate under such conditions: there is no elastic medium in vacuum, and elastic mechanical vibrations cannot arise. As a rule, sound travels slower in gases, slightly faster in liquids, and fastest in solids.

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 / s):

The speed of sound in some liquids at 20 °C is (m/s):

Longitudinal and transverse elastic waves propagate in a solid medium, and the velocity of the longitudinal waves is always greater than that of the transverse waves. The speed of sound in some solids is (m/s):

Today, many new settlers, equipping an apartment, are forced to carry out additional work, including soundproofing their homes, because. the standard materials used make it possible only to partially hide what is happening in one's own house, and not to be interested against the will in the communication of neighbors.

In solids, at least the density and elasticity of the substance opposing the wave affects. Therefore, when equipping the premises, the layer adjacent to the load-bearing wall is made soundproof with "laps" from above and below. It allows you to reduce in decibels sometimes more than 10 times. Then basalt mats are laid, and plasterboard sheets are laid on top, which reflect the sound outward from the apartment. When a sound wave “flies up” to such a structure, it is attenuated in the insulator layers, which are porous and soft. If the sound is strong, then the materials that absorb it may even heat up.

Elastic substances, such as water, wood, metals, transmit well, so we hear a wonderful "singing" musical instruments. And some nationalities in the past determined the approach, for example, of riders, putting their ear to the ground, which is also quite elastic.

The speed of sound in km depends on the characteristics of the medium in which it propagates. In particular, the process can be affected by its pressure, chemical composition, temperature, elasticity, density and other parameters. For example, in a steel sheet, a sound wave travels at a speed of 5100 meters per second, in glass - about 5000 m / s, in wood and granite - about 4000 m / s. To convert speed to kilometers per hour, multiply by 3600 (seconds per hour) and divide by 1000 (meters per kilometer).

The speed of sound in km in the aquatic environment 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, it is already about 1490 m/s.

The saline environment is distinguished by a deliberately higher speed of passage of sound vibrations.

The propagation of sound in air also depends on temperature. With the value of this parameter equal to 20, sound waves travel 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 learn that in a material such as cork, which is often used to reduce outside noise, the speed of sound in km is only 1800 km/h (500 meters per second). This is ten times lower than this characteristic in steel parts.

A sound wave is a longitudinal vibration of the medium in which it propagates. When passing, for example, a melody piece of music through some obstacle, its volume level decreases, because. changes At the same time, the frequency remains the same, due to which we hear the female voice as female, and the male voice as male. The most interesting is the place where the speed of sound in km is close to zero. This is a vacuum in which waves of this type hardly propagate. To demonstrate how this works, physicists place a ringing alarm clock under a hood that is deflated. The greater the rarefaction of the air, the quieter the call is heard.