Speed ​​of sound propagation in water. How much is the speed of sound in km per hour

For sound to propagate, an elastic medium is required. In a vacuum, sound waves cannot propagate, since there is nothing there to vibrate. This can be verified by simple experience. If you place an electric bell under a glass bell, then as the air is pumped out from under the bell, the sound from the bell will become weaker and weaker until it stops completely.

It is known that during a thunderstorm we see a flash of lightning and only after a while we hear the rumble of thunder. This delay occurs because the speed of sound in air is much less than the speed of light coming from lightning.

The speed of sound in air was first measured in 1636 by the French scientist M. Mersenne. At a temperature of 20 °C it is equal to 343 m/s, i.e. 1235 km/h. Note that it is to this value that the speed of a bullet fired from a Kalashnikov assault rifle decreases at a distance of 800 m. Initial speed bullets 825 m/s, which significantly exceeds the speed of sound in air. Therefore, a person who hears the sound of a shot or the whistle of a bullet need not worry: this bullet has already passed him. The bullet outruns the sound of the shot and reaches its victim before the sound arrives.

The speed of sound in gases depends on the temperature of the medium: with an increase in air temperature it increases, and with a decrease it decreases. At 0 °C, the speed of sound in air is 332 m/s.

In different gases, sound travels with at different speeds. The greater the mass of gas molecules, the less speed sound in it. Thus, at a temperature of 0 °C, the speed of sound in hydrogen is 1284 m/s, in helium - 965 m/s, and in oxygen - 316 m/s.

The speed of sound in liquids is usually greater than the speed of sound in gases. The speed of sound in water was first measured in 1826 by J. Colladon and J. Sturm. They carried out their experiments on Lake Geneva in Switzerland. On one boat they set fire to gunpowder and at the same time struck a bell lowered into the water. The sound of this bell, lowered into the water, was caught on another boat, which was located at a distance of 14 km from the first. Based on the time interval between the flash of the light signal and the arrival of the sound signal, the speed of sound in water was determined. At a temperature of 8°C it turned out to be equal to 1440 m/s.

The speed of sound in solids is greater than in liquids and gases. If you put your ear to the rail, then after hitting the other end of the rail, two sounds are heard. One of them reaches the ear by rail, the other by air.

The earth has good sound conductivity. Therefore, in the old days, during a siege, “listeners” were placed in the fortress walls, who, by the sound transmitted by the earth, could determine whether the enemy was digging into the walls or not. Putting their ears to the ground, they also monitored the approach of enemy cavalry.

Solids conduct sound well. Thanks to this, people who have lost their hearing are sometimes able to dance to music that reaches the auditory nerves not through the air and the outer ear, but through the floor and bones.

The speed of sound can be determined by knowing the wavelength and frequency (or period) of vibration.

Our universe rests on such elementary and fundamental constants as sound and light speed; these are axioms in the world of physics. It is clear that we have all thought about the question - what do these speeds depend on? When we observe lightning, we first see the light, and then the roar comes to us. Why does this happen and what determines the time that passes from flash to thunder? In fact, everything is very simple and easy to explain, you just need to remember some basic provisions from school course physicists, they will put everything in its place, well, almost everything... But first things first...

What is the speed of light

Light spreads - 299,792,458 m/s, in the more familiar kilometer equivalent it is 1,079,252,848.8 km/h, but for ease of operation, this complex figure is usually rounded and considered to be 300 thousand km/s. The speed of light is the maximum speed at which something can propagate in our universe. But the most interesting thing about all this is that it is absolutely independent of the speed of the source emitting it. How are things going in our world? The difference in the pace of the thrown body and the object from which it was thrown can increase or decrease, depending on the acceleration at which the throw was made. Let's look at an example: you are driving a car whose speed is 100 km per hour and throw a stone in the direction of travel (let's assume the speed of the thrown stone is 10 km/h), for an outside observer who is standing on the side of the road, the stone will fly at a speed of - 110 km/h. In this case, the speed of the throw and the car are summed up. But this does not apply to the speed of light. No matter which direction the source flies, the light will travel at the same speed; it will not speed up or slow down. This is the paradox. At least that's what they thought before, but what is the situation now? More on this a little later...

What is faster - the speed of light or the speed of sound?

Scientists know that the speed of light is about a million times faster than sound. But the tempo of the sound can change. Its average value is 1450 m/s. The speed at which sound travels depends on the type of medium, whether it is water or air, on temperature and even pressure. It turns out that exact value this value does not exist, there is only an approximate value in our familiar environment - air. Regarding the speed of light, whole series of experiments are still being conducted by advanced scientists from all over the planet.

What is the speed of sound in air

The French scientist M. Mersenne managed to determine the speed of sound in air for the first time in 1636. Temperature environment was 20 °C and with this indicator the sound flew with a value of 343 m/s, in kilometers - 1235 km/h. The rate of movement of sound directly depends on the temperature of the environment in which it propagates: if the temperature of the gas increases, the sound also begins to move faster, respectively, on the contrary, the lower the air temperature, the slower the sound travels.

For example, at zero temperature, sound is transmitted at a speed of 331 m/s. The speed of sound also depends on the type of gas. The larger the diameter of the molecules that make up a gas, the slower the sound moves. For example, at zero temperature, in hydrogen the speed of sound will be 1284 m/s, in helium - 965 m/s. Noticeable difference.

Speed ​​of sound in vacuum

Sound, at its core, is the vibration of molecules as they travel. It is clear that in order for sound to be somehow transmitted, a medium of molecules is needed that will vibrate. In a vacuum there is no matter, so sound cannot pass there. But according to the results of recent research, it has become clear that sound can overcome a layer of vacuum less than a micron thick. This phenomenon was called “vacuum phonon tunneling”, information on it appeared simultaneously in two articles that appeared in printed edition"Physical Review Letters". It should be remembered that the vibration of molecules crystal lattice carry not only sound, but also thermal energy Therefore, heat can also be transferred through a vacuum.

Speed ​​of sound in water

Typically, the speed of sound in liquids, including water, is greater than in a gaseous medium. The first measurement of such rapidity in water was made in 1826 by scientists J. Colladon and J. Sturm. The experiment took place in Switzerland, namely on one of the lakes. The sequence of actions followed by the measurement was as follows:

1. On a boat that was anchored, a bag of gunpowder was set on fire and at the same time the underwater bell was struck;
2. At a distance of 14 kilometers there was a second observation boat, in addition to the flash of gunpowder, which was visible from afar, the sound of the bell was also caught on the boat through an underwater horn;
3. It was from the time difference between the flash and the arrival of the sound wave that it was possible to calculate the speed of sound. Then the water had a temperature of 8 ° C and the speed of sound was 1440 m/s.

Between two different media, a sound wave behaves interestingly. One part of it enters another medium, the second is simply reflected. If sound enters a liquid from air, then 99.9% of it is reflected, but the pressure in that fraction of sound that still passes into the water doubles. This is exactly what fish use. If you scream and make noise near the water, the tailed inhabitants of the depths will quickly go far away.

Speed ​​of sound

Even light, as well as sound and electromagnetic vibrations, can change their speed in different physical environments. The latest research in this area has proven the theoretical possibility of launching a body faster than light. The fact is that in some gases the speed of photons (the particles that make up light) slows down noticeably. It is clear that such a phenomenon cannot be seen with the naked eye, but in exact science, such as physics, it is of great importance. So, scientists have proven that if you pass light through a gas, its speed will decrease so much that a rapidly launched body can move faster than photons.

Discuss the propagation of sound in different environments

Most people understand perfectly well what sound is. It is associated with hearing and is associated with physiological and psychological processes. The brain processes sensations that come through the hearing organs. The speed of sound depends on many factors.

Sounds distinguished by people

IN in a general sense words sound is physical phenomenon, which causes effects on the hearing organs. It has the form of longitudinal waves of different frequencies. People can hear sound whose frequency ranges from 16-20,000 Hz. These elastic longitudinal waves, which propagate not only in air, but also in other media, reaching the human ear, cause sound sensations. People can't hear everything. Elastic waves with a frequency of less than 16 Hz are called infrasound, and those above 20,000 Hz are called ultrasound. The human ear cannot hear them.

Sound characteristics

There are two main characteristics of sound: volume and pitch. The first of them is related to the intensity of the elastic sound wave. There is another important indicator. Physical size, which characterizes the height, is the oscillation frequency of the elastic wave. In this case, one rule applies: the larger it is, the higher the sound, and vice versa. One more the most important characteristic is the speed of sound. It varies in different environments. It represents the speed of propagation of elastic sound waves. In a gaseous environment this figure will be less than in liquids. The speed of sound in solids is the highest. Moreover, for longitudinal waves it is always greater than for transverse ones.

Speed ​​of propagation of sound waves

This indicator depends on the density of the medium and its elasticity. In gaseous media it is affected by the temperature of the substance. As a rule, the speed of sound does not depend on the amplitude and frequency of the wave. In rare cases when these characteristics have an influence, they speak of so-called dispersion. The speed of sound in vapors or gases ranges from 150-1000 m/s. In liquid media it is already 750-2000 m/s, and in solid materials - 2000-6500 m/s. IN normal conditions the speed of sound in air reaches 331 m/s. IN ordinary water- 1500 m/s.

Speed ​​of sound waves in different chemical media

The speed of sound propagation in different chemical media is not the same. So, in nitrogen it is 334 m/s, in air - 331, in acetylene - 327, in ammonia - 415, in hydrogen - 1284, in methane - 430, in oxygen - 316, in helium - 965, in carbon monoxide- 338, in carbon dioxide - 259, in chlorine - 206 m/s. The speed of a sound wave in gaseous media increases with increasing temperature (T) and pressure. In liquids, it most often decreases as T increases by several meters per second. Speed ​​of sound (m/s) in liquid media (at a temperature of 20°C):

Water - 1490;

Ethyl alcohol - 1180;

Benzene - 1324;

Mercury - 1453;

Carbon tetrachloride - 920;

Glycerin - 1923.

The only exception to the above rule is water, in which the speed of sound increases with increasing temperature. It reaches its maximum when this liquid is heated to 74°C. With a further increase in temperature, the speed of sound decreases. As the pressure increases, it will increase by 0.01%/1 Atm. In the salty sea ​​water As temperature, depth and salinity increase, the speed of sound will also increase. In other environments, this indicator changes differently. Thus, in a mixture of liquid and gas, the speed of sound depends on the concentration of its components. In an isotopic solid, it is determined by its density and elastic moduli. Transverse (shear) and longitudinal elastic waves propagate in unconfined dense media. Speed ​​of sound (m/s) in solids (longitudinal/transverse waves):

Glass - 3460-4800/2380-2560;

Fused quartz - 5970/3762;

Concrete - 4200-5300/1100-1121;

Zinc - 4170-4200/2440;

Teflon - 1340/*;

Iron - 5835-5950/*;

Gold - 3200-3240/1200;

Aluminum - 6320/3190;

Silver - 3660-3700/1600-1690;

Brass - 4600/2080;

Nickel - 5630/2960.

In ferromagnets, the speed of the sound wave depends on the strength of the magnetic field. In single crystals, the speed of a sound wave (m/s) depends on the direction of its propagation:

• ruby (longitudinal wave) - 11240;
• cadmium sulfide (longitudinal/transverse) - 3580/4500;
• lithium niobate (longitudinal) - 7330.

The speed of sound in a vacuum is 0, since it simply does not propagate in such a medium.

Determination of the speed of sound

Everything that is associated with sound signals, interested our ancestors thousands of years ago. Almost all outstanding scientists worked to determine the essence of this phenomenon. ancient world. Even ancient mathematicians established that sound is caused by the oscillatory movements of the body. Euclid and Ptolemy wrote about this. Aristotle established that the speed of sound has a finite value. The first attempts to determine this indicator were made by F. Bacon in the 17th century. He tried to establish the speed by comparing the time intervals between the sound of the gunshot and the flash of light. Based on this method, a group of physicists at the Paris Academy of Sciences first determined the speed of a sound wave. IN different conditions experiment it was 350-390 m/s. The theoretical justification of the speed of sound was first considered by I. Newton in his “Principles”. P.S. was able to correctly determine this indicator. Laplace.

Sound speed formulas

For gaseous media and liquids in which sound propagates, as a rule, adiabatically, the temperature change associated with tension and compression in a longitudinal wave cannot quickly equalize over time. short period time. Obviously, this indicator is influenced by several factors. The speed of a sound wave in a homogeneous gaseous medium or liquid is determined by the following formula:

where β is adiabatic compressibility, ρ is the density of the medium.

In partial derivatives, this quantity is calculated using the following formula:

c 2 = -υ 2 (δρ/δυ) S = -υ 2 Cp/Cυ (δρ/δυ) T,

where ρ, T, υ - the pressure of the medium, its temperature and specific volume; S - entropy; Cp - isobaric heat capacity; Cυ - isochoric heat capacity. For gas media this formula will look like this:

c 2 = ζkT/m= ζRt/M = ζR(t + 273.15)/M = ά 2 T,

where ζ is the adiabatic value: 4/3 for polyatomic gases, 5/3 for monatomic gases, 7/5 for diatomic gases (air); R - gas constant (universal); T- absolute temperature, measured in kelvins; k is Boltzmann's constant; t - temperature in °C; M- molar mass; m- molecular weight; ά 2 = ζR/ M.

Determination of the speed of sound in a solid

In a solid body that is homogeneous, there are two types of waves that differ in the polarization of vibrations in relation to the direction of their propagation: transverse (S) and longitudinal (P). The speed of the first (C S) will always be lower than the second (C P):

C P 2 = (K + 4/3G)/ρ = E(1 - v)/(1 + v)(1-2v)ρ;

C S 2 = G/ρ = E/2(1 + v)ρ,

where K, E, G - compression, Young, shear moduli; v - Poisson's ratio. When calculating the speed of sound in a solid, adiabatic elastic moduli are used.

Speed ​​of sound in multiphase media

In multiphase media, due to inelastic absorption of energy, the speed of sound is directly dependent on the vibration frequency. In a two-phase porous medium, it is calculated using the Bio-Nikolaevsky equations.

Conclusion

Measuring the speed of a sound wave is used to determine various properties of substances, such as the modulus of elasticity of a solid, the compressibility of liquids and gases. A sensitive method for detecting impurities is to measure small changes in sound wave speed. In solids, the fluctuation of this indicator allows one to study the band structure of semiconductors. The speed of sound is a very important quantity, the measurement of which allows us to learn a lot about a wide variety of media, bodies and other objects scientific research. Without the ability to determine it, many scientific discoveries would be impossible.

The warmer the water, the faster the speed of sound. When diving to greater depths, the speed of sound in water also increases. Kilometers per hour (km/h) is a non-system unit of speed measurement.

And in 1996, the first version of the site with instant calculations was launched. Already in ancient authors there is an indication that sound is caused by oscillatory movement bodies (Ptolemy, Euclid). Aristotle notes that the speed of sound has a finite value, and correctly imagines the nature of sound.

Speed ​​of sound in gases and vapors

In multiphase media, due to the phenomena of inelastic energy absorption, the speed of sound, generally speaking, depends on the oscillation frequency (that is, velocity dispersion is observed). For example, speed estimation elastic waves in a two-phase porous medium can be performed using the equations of the Bio-Nikolaevsky theory. When enough high frequencies(above the Biot frequency) in such a medium not only longitudinal and transverse waves arise, but also a longitudinal wave of the second kind.

IN clean water the speed of sound is about 1500 m/s (see the Colladon-Sturm experiment) and increases with increasing temperature. An object moving at a speed of 1 km/h travels one kilometer in one hour. If you do not find yourself in the list of suppliers, notice an error, or have additional numerical data for colleagues on the topic, please let us know.

The information presented on the site is not official and is provided for informational purposes only. On earth passage shock wave is perceived as a clap, similar to the sound of a gunshot. Having exceeded the speed of sound, the plane passes through this area of ​​​​increased air density, as if piercing it - breaking the sound barrier. For a long time breaking the sound barrier seemed to be a serious problem in the development of aviation.

flight Mach numbers M(∞), slightly higher than the critical number M*. The reason is that at numbers M(∞) > M* a wave crisis occurs, accompanied by the appearance of wave resistance. 1) gates in fortresses.

Why is it dark in space? Is it true that stars fall? A speed whose Mach number exceeds 5 is called hypersonic. Supersonic speed is the speed of movement of a body (gas flow) exceeding the speed of sound under identical conditions.

See what “SUPERSONIC SPEED” is in other dictionaries:

IN solids sound travels much faster than in water or air. A wave is, in a sense, the movement of something spreading in space. A wave is a process of movement in space of state change. Let's imagine how sound waves propagate in space. These layers are compressed, which in turn again creates overpressure, affecting neighboring layers of air.

This phenomenon is used in ultrasonic flaw detection of metals. The table shows that as the wavelength decreases, the size of defects in the metal (cavities, foreign inclusions) that can be detected by an ultrasound beam decreases.

The fact is that when moving at flight speeds above 450 km/h, wave drag begins to be added to the usual air resistance, which is proportional to the square of the speed. Wave drag increases sharply as the aircraft speed approaches the speed of sound, several times higher than the drag associated with friction and the formation of vortices.

What is the speed of sound?

In addition to speed, wave resistance directly depends on the shape of the body. So, the swept wing noticeably reduces the wave drag. A further increase in the angle of attack during maneuvering leads to the spread of stall throughout the entire wing, loss of controllability and stalling of the aircraft into a tailspin. A forward-swept wing is partially free of this drawback.

When creating a forward-swept wing, complex problems arose, primarily associated with elastic positive divergence (or simply with twisting and subsequent destruction of the wing). Wings made of aluminum and even steel alloys blown through supersonic tubes were destroyed. It wasn't until the 1980s that composite materials emerged that could combat twisting by using specially oriented windings of carbon fibers.

For sound to propagate, an elastic medium is required. In a vacuum, sound waves cannot propagate, since there is nothing there to vibrate. At a temperature of 20 °C it is equal to 343 m/s, i.e. 1235 km/h. Note that it is to this value that the speed of a bullet fired from a Kalashnikov assault rifle decreases at a distance of 800 m.

Sound travels at different speeds in different gases. Enter the value you want to convert (speed of sound in air). In the regions modern technologies and the one who manages to do everything quickly wins the business.

Speed ​​of sound- the 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 a 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, we speak of sound dispersion.

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  Already in ancient authors there is an indication that sound is caused by 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 to experimentally determine the speed of sound 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 gunshot. Using this method, various researchers (M. Mersenne, P. Gassendi, W. Derham, a group of scientists from the Paris Academy of Sciences - D. Cassini, J. Picard, Huygens, Roemer) determined the value of the speed of sound (depending on the experimental conditions, 350- 390 m/s). Theoretically, the question of the speed of sound was first considered by I. Newton in his “Principles”. Newton actually assumed that sound propagation is isothermal, and therefore received an underestimate. The correct theoretical value for the speed of sound 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 = 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 (C_(p))(C_(v)))\left((\ frac (\partial p)(\partial v))\right)_(T))))

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

  For solutions and other complex physicochemical 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 via surface waves 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 body waves.