What is the speed of sound in km per hour? What is the speed of sound?
Sound speed
The main characteristics of sound waves include the speed of sound, its intensity - these are the objective characteristics of sound waves, pitch, loudness are classified as subjective characteristics. Subjective characteristics depend to a large extent on the perception of the sound by a particular person, and not on the physical characteristics of the sound.
Measurements of the speed of sound in solids, liquids and gases indicate that the speed does not depend on the frequency of vibration or the length of the sound wave, i.e., sound waves do not have dispersion. Longitudinal and transverse waves can propagate in solids, the speed of propagation of which is found using the formulas:
where E is Young's modulus, G is shear modulus in solids. In solids, the speed of propagation of longitudinal waves is almost twice as large as the speed of propagation of transverse waves.
Only longitudinal waves can propagate in liquids and gases. The speed of sound in water is found using the formula:
K is the bulk modulus of the substance.
In liquids, as the temperature increases, the speed of sound increases, which is associated with a decrease in the volumetric compression ratio of the liquid.
For gases, a formula has been derived that relates their pressure to density:
I. Newton was the first to use this formula to find the speed of sound in gases. From the formula it is clear that the speed of sound propagation in gases does not depend on temperature, it also does not depend on pressure, since as pressure increases, the density of the gas also increases. The formula can also be given a more rational form: based on the Mendeleev-Clapeyron equation:
Then the speed of sound will be equal to:
The formula is called Newton's formula. The speed of sound in air calculated with its help is 280 m/s at 273K. The actual experimental speed is 330 m/s.
This result differs significantly from the theoretical one, and the reason for this was established by Laplace.
He showed that sound propagates adiabatically in air. Sound waves in gases travel so quickly that the created local changes in volume and pressure in the gas environment occur without heat exchange with the environment. Laplace derived an equation for finding the speed of sound in gases:
Propagation of sound waves
As sound waves propagate through the medium, they attenuate. The amplitude of vibrations of particles of the medium gradually decreases with increasing distance from the sound source.
One of the main reasons for the attenuation of waves is the action of internal friction forces on the particles of the medium. To overcome these forces, the mechanical energy of oscillatory motion, which is transferred by the wave, is continuously used. This energy turns into the energy of chaotic thermal movement of molecules and atoms of the environment. Since the wave energy is proportional to the square of the oscillation amplitude, as the waves propagate from the sound source, along with a decrease in the energy reserve of the oscillatory motion, the oscillation amplitude also decreases.
The propagation of sounds in the atmosphere is influenced by many factors: temperature at different altitudes, air flows. Echo is sound reflected from a surface. Sound waves can be reflected from solid surfaces, from layers of air in which the temperature is different from the temperature of neighboring layers.
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 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.
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, estimation of the velocity of elastic waves in a two-phase porous medium can be performed using the equations of the Bio-Nikolaevsky theory. At sufficiently high frequencies (above the Biot frequency), not only longitudinal and transverse waves, but also a longitudinal wave of the second kind arise in such a medium.
In pure 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 the ground, the passage of the shock wave is perceived as a bang, 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:
Sound travels much faster in solids 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 excess pressure, 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. 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 areas of modern technology and business, the winner is the one who manages to do everything quickly.
The first attempts to understand the nature of the origin of sound were made more than two thousand years ago. In the works of the ancient Greek scientists Ptolemy and Aristotle, correct assumptions are made that sound is generated by body vibrations. Moreover, Aristotle argued that the speed of sound is a measurable and finite quantity. Of course, in Ancient Greece there were no technical capabilities for any accurate measurements, so the speed of sound was measured relatively accurately only in the seventeenth century. For this purpose, a comparison method was used between the time of detection of the flash from the shot and the time after which the sound reached the observer. As a result of numerous experiments, scientists came to the conclusion that sound travels in the air at a speed of 350 to 400 meters per second.
The researchers also found that the speed of propagation of sound waves in a particular medium directly depends on the density and temperature of this medium. So, the thinner the air, the slower sound travels through it. In addition, the higher the temperature of the medium, the higher the speed of sound. Today it is generally accepted that the speed of propagation of sound waves in air under normal conditions (at sea level at a temperature of 0ºC) 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 it is usual, the environmental characteristics are very different from normal. This is why aviation uses a universal concept called the Mach number, named after the Austrian Ernst Mach. This number represents 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 higher the Mach number will be, even if the speed of the object itself does not change.
The practical application of this number is due to the fact that movement at speeds that are higher than the speed of sound is significantly different from movement at subsonic speeds. This is mainly due to changes in the aerodynamics of the aircraft, deterioration in its controllability, heating of the body, as well as wave resistance. These effects are observed only when the Mach number exceeds one, that is, the object breaks 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.
Video on the topic
Sources:
- Tuning fork vibration frequency 440 Hz
Various physical objects that are in a solid, liquid or gaseous state can sound. For example, a vibrating string or a stream of air blown from a pipe.
Sound is wave vibrations of the medium perceived by the human ear. The sources are various physical bodies. The vibration of the source excites vibrations in the environment, which propagate in space. Sound waves occupy a frequency range from 20 Hz to 20 kHz, between infrasound and ultrasound.
Mechanical vibrations occur only where there is elastic vibration, so sound cannot travel in a vacuum. The speed of sound is the speed at which a sound wave travels around the sound source.
Sound travels through gases, liquids and solids at different speeds. Sound travels faster in water than in air. In solids the speed of sound is higher than in . For each substance, the speed of sound propagation is constant. Those. the speed of sound depends on the density and elasticity of the medium, and not on the frequency of the sound wave and its amplitude.
The sound one can go around the obstacle it encounters. This is called diffraction. Low sounds have better diffraction than high sounds. Here
Today, many new settlers, when furnishing an apartment, are forced to carry out additional work, including soundproofing their home, because... The standard materials used make it possible to only partially hide what is going on in your own home, and not to be interested in the communication of your neighbors against your will.
In solids, it is affected at least by the density and elasticity of the substance resisting the wave. Therefore, when equipping premises, the layer adjacent to the load-bearing wall is made soundproof with “overlaps” at the top and bottom. It allows you to reduce decibels sometimes by more than 10 times. Then basalt mats are laid, and plasterboard sheets are placed 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, the materials that absorb it may even heat up.
Elastic substances, such as water, wood, and metals, transmit well, so we hear the beautiful “singing” of musical instruments. And some peoples in the past determined the approach of, for example, horsemen, by 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, you need to multiply the figures by 3600 (seconds per hour) and divide by 1000 (meters per kilometer).
The speed of sound in km in an aquatic environment is different for substances with different salinities. 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.
A salty environment is characterized by a obviously higher speed of sound vibrations.
The propagation of sound in air also depends on temperature. With a value of 20 for this parameter, 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 external noise levels, 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, for example, the melody of a piece of music passes through some obstacle, its volume level decreases, because changes. At the same time, the frequency remains the same, thanks to which we hear a woman’s voice as a woman’s, and a man’s as a man’s. The most interesting place is where the speed of sound in km is close to zero. This is a vacuum in which waves of this type almost do not propagate. To demonstrate how this works, physicists place a ringing alarm clock under a hood from which the air is pumped out. The thinner the air, the quieter the bell is heard.
The observer used a watch to note the time elapsed between the appearance of the flash and the moment when the sound was heard. The time it took the light to travel this distance was neglected. In order to eliminate the influence of the wind as much as possible, there was a cannon and an observer on each side, and each cannon fired at approximately the same time.
The average value of two time measurements was taken, and based on it. It turned out to be approximately equal to 340 ms -1. The big disadvantage of this method of measurement was that the gun was not always at hand!
Many examinees describe a similar method. One student stands on one side of the football field with a starting pistol, and the other stands on the other side with a stopwatch. The distance between them is carefully measured with a tape measure. The student starts the stopwatch when he sees smoke coming from the barrel and stops it when he hears the sound. The same is done when they switch places to compensate for the effects of the wind. Then the average time is determined.
Since sound travels at 340 ms -1 , a stopwatch will likely not be accurate enough. It is preferable to operate in centiseconds or milliseconds.
Measuring the speed of sound using echo
When a short sharp sound, such as a clap, is produced, the wave impulse can be reflected by a large obstacle, such as a wall, and heard by an observer. This reflected impulse is called an echo. Let's imagine that a person stands at a distance of 50 m from the wall and makes one clap. When the echo is heard, the sound has traveled 100 m. Measuring this interval with a stopwatch will not be very accurate. However, if a second person holds a stopwatch and the first person claps, then the time for a large number of echo sounds can be obtained with reasonable accuracy.
Suppose that the distance at which the clapping person is in front of the wall is 50 m, and the time interval between the first and one hundred and first clap is 30 s, then:
sound speed= distance traveled / time of one clap = 100m: 30 / 100 s = 333 ms -1
Measuring the speed of sound using an oscilloscope
A more sophisticated way to directly measure the speed of sound is to use an oscilloscope. The loudspeaker emits pulses at regular intervals, and they are recorded by a cathode ray oscilloscope (see figure). When a pulse is received by the microphone, it will also be recorded by the oscilloscope. If the timing characteristics of the oscilloscope are known, the time interval between two pulses can be found.
The distance between the loudspeaker and microphone is measured. The speed of sound can be found using the formula speed = distance / time.
Speed of sound in various media
The speed of sound is higher in solids than in liquids and higher in liquids than in gases. Past experiments on Lake Geneva have shown that the speed of sound in water is significantly higher than in air. In fresh water, the speed of sound is 1410 ms -1, in sea water - 1540 ms -1. In iron, the speed of sound is approximately 5000 ms -1.
By sending sound signals and noting the time interval before the arrival of the reflected signal (echo), it is possible to determine the depth of the sea and the location of schools of fish. During the war, high-frequency sounders were used to detect mines. Bats in flight use a special form of echo to detect obstacles. The bat emits a high-frequency sound that bounces off an object in its path. The mouse hears the echo, locates the object and avoids it.
The speed of sound in air depends on atmospheric conditions. The speed of sound is proportional to the square root of pressure divided by density. Changes in pressure do not affect the speed of sound in air. This is because an increase in pressure entails a corresponding increase in density and the ratio of pressure to density remains constant.
The speed of sound in air (as in any gas) is affected by temperature changes. The laws for gases indicate that the ratio of pressure to density is proportional to . Thus, the speed of sound is proportional to √T. It is easier to break the sound barrier at higher altitudes because the temperature is lower there.
The speed of sound is affected by changes in humidity. The density of water vapor is less than the density of dry air at the same pressure. At night, when humidity rises, sound travels faster. Sounds are heard more clearly on a quiet, foggy night.
This is partly due to the increased humidity, and partly because in these conditions there is usually a temperature inversion, in which sounds are refracted in such a way that they do not dissipate.
