What exactly is the 'sound velocity' that humanity has longed for?

Light is the fastest in the universe, and its speed reaches 300,000 kilometers per second. However, on the earth, the ' sonic velocity ' of about 340 meters per second is the speed barrier, and humankind has been studying how airplanes can overcome the speed barrier. Such velocity of sound is explained by ZME Science, a science news site.

What, really, is the speed of sound?


What we perceive as sound is basically movement and vibration of particles, and the most common is vibration caused by particles in the atmosphere. For example, “speaking aloud” is possible because the air pushed out of the lungs collides with the vocal cords and vibrates. Then, the vibration collides with the eardrum in the ear of the other person, and the vibration transmitted to the eardrum is converted into an electric signal and processed by the brain, so that the person can 'listen'.

From a physics point of view, sound behaves like a wave rushing to the beach. The loudness is determined by the wave height (amplitude), and the pitch is determined by the frequency (frequency) at which the waves hit the shore. The farther the wave goes, the less energy it has and eventually the sound disappears. That's why you can't hear the sounds behind the earth.

Also, how sound is transmitted depends on the ' medium ' that transmits the waves. If you look at the movie below, you can clearly see how sound is transmitted differently for solids, liquids, and gases.

Speed propagation with animated dominoes-Why speed is fastest in solids-YouTube

Conversely, if there is no medium to transmit sound, no sound will be transmitted. For example, if you scream something in outer space, no one can hear you. However, if you put space suits on top of each other so that vibrations can be transmitted, you will be able to convey your voice.

Furthermore, how the sound is transmitted also changes depending on the elasticity of the medium. Elasticity is characterized by resistance to bending and twisting ( rigidity ) and the limit of how much it can deform ( elasticity limit ). Both iron and rubber have elasticity, but iron has a high rigidity and rubber has a high elastic limit. Of course, the way sound is transmitted differs greatly between iron and rubber.

In other words, how sound is transmitted greatly changes depending on the elasticity and density of the medium. For example, hydrogen and oxygen have almost the same elasticity, but hydrogen has a lower density. However, the speed of sound when using hydrogen as the medium is approximately 1270 meters per second, but when using oxygen as the medium, it is approximately 326 meters per second. Also, although iron has a much higher density, it is also highly elastic, so the speed of sound transmitted through the iron can reach up to about 5120 meters per second.

In the atmosphere around us, sound basically travels at about 340 meters per second, although it changes with temperature. When pursuing the speed of an airplane, this 340 meters per second stands as a 'sonic wall'. One of the reasons why the speed of sound is a barrier to the pursuit of speed is the occurrence of the sonic boom .

You can see how an airplane flying above the speed of sound generates a shock wave and a sonic boom in the following movie.

Supersonic Flight, Sonic Booms-YouTube

An airplane moving faster than the speed of sound will compress the air in front of you. Eventually, all of this compressed air is blown off the nose of an airplane at Mach 1 (the speed of sound traveling through the atmosphere). Anyone within reach of this blast of ultra-compressed air will hear a loud sound called a sonic boom. However, because the plane is flying above the speed of sound, the sonic boom can only be heard 'after the plane passes in front of the observer.'

It was relatively recent that mankind was able to exceed the speed of sound, recorded in 1947. While sonic flight over land is basically banned in the United States and Europe, 'supersonic flight remains an important topic in the pursuit of aircraft technology,' ZME Science said.

in Science,   Video, Posted by log1i_yk