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Ultrasound and infrasound contrast

Ultrasound and infrasound contrastFirst, the ultrasonic
1, the frequency higher than the upper limit of human hearing (about 20000Hz) sound waves, called ultrasound. Ultrasound in the medium of reflection, refraction, diffraction, scattering, propagation, and the audible sound of the law does not fundamentally different. But the ultrasonic wavelength is very short, only a few centimeters, or even thousandths of a millimeter. Compared with the audible sound waves.
2, ultrasound has many strange features: the propagation characteristics - the ultrasonic wavelength is very short, usually the size of obstacles than the ultrasonic wavelength of good times, so the ultrasonic diffraction ability is poor, it can be oriented in a homogeneous medium, a straight line , the shorter the wavelength of ultrasound, a feature the more remarkable. Power characteristics - when the propagation of sound in air, push the air back and forth vibration of particles acting on the particles, acoustic power is that the speed of sound as a function of physical quantities. At the same intensity, the higher the frequency of sound waves, the greater the power it has. As the ultrasonic frequency is high, so the ultrasonic sound waves compared with the general, and its power is very large. Cavitation - When the ultrasonic propagation in liquids, due to severe vibration of liquid particles, generated in the liquid inside small cavities. These small holes quickly swell and close, make the liquid particles between the collision effect, resulting in thousands to tens of thousands of atmospheres of pressure. This intense interaction between the particles will lead to a sudden increase in temperature of the liquid, stirring well to play the role, so that the two kinds of immiscible liquids (water and oil) emulsion occurred, and to accelerate the dissolution of the solute accelerate chemical reaction. This effect in the liquid by the ultrasonic various effects caused by ultrasonic cavitation is called.
3, able to transmit and receive ultrasound animals: bats, mosquitoes, cats, dogs, such as the West with a dog whistle to call his dog. 
Second, infrasound
1, also known as sub-sub-sonic sound waves, it is a sound wave frequencies below the human audible frequency range of sound waves. Infrasound frequency range of roughly 10-4Hz ~ 20Hz. Infrasound generated sound source is quite extensive, it is now known to have a second sound source: volcanic eruptions, meteor crashed into the atmosphere, aurora, earthquakes, tsunamis, typhoons, thunderstorms, tornadoes, ionospheric disturbances, and so on. The use of artificial methods can produce infrasound, such as nuclear explosions, rocket launchers, chemical explosions, and so on.
2, due to very low frequency infrasound, so it shows all sorts of peculiar nature. The most notable feature is the transmission distance, and not easily absorbed. We know that the sound attenuation in the atmosphere, mainly by molecular absorption, heat conduction and viscous effects caused by the corresponding absorption coefficient is proportional to the square wave frequency. Because infrasound very low frequencies, so the atmosphere in the dissemination process of the absorption coefficient is very small it. For example, a frequency of 0.1Hz air on the absorption coefficient of the sub-sonic frequency of 1000Hz is about the sound absorption coefficient of the 100 million one. As the second wave is not easily absorbed, so it's spread very far away. August 27, 1883, when Indonesia's Krakatoa volcano eruption, it generates a second wave around the earth three times, spread more than ten thousands of meters. At the time, people use a simple micro-barometer had recorded it. Infrasound is not only "running" too far, and it spread faster than the speed of the storm, so it became the prelude to the advent of ocean storms, people can use infrasound to forecast turmoil.
3, the second wave of applications starting from the 1950s, and gradually widely valued by the people. Second wave of applications generally have the following aspects:
(1) through the study of natural phenomena arising from the sub-sonic features and the production mechanism, more in-depth study and understanding of the characteristics of these natural phenomena and laws. For example, the use of infrasound generated by the aurora, auroral activity can study the law.
(2) measured using the received sound source generated infrasound, can detect the sound source location, size, and study other features. For example, by receiving nuclear explosions, rocket launchers or typhoon generated infrasound to detect these times of the sound source parameters. (3) prediction of natural catastrophic events. Many disasters of natural phenomena, such as volcanic eruptions, tornadoes, thunderstorms, typhoons, etc., may be in place before the radiation of infrasound, it is possible to use these precursor phenomena to predict natural disasters and forecasting these events. 
(4) times a sound wave propagation in the atmosphere, the atmosphere is very susceptible to media influence, with the atmosphere of such factors as wind and temperature distribution are closely linked. Thus, by measuring the natural or artificial can be generated infrasound propagation characteristics in the atmosphere, to detect the nature of some large-scale weather and laws. The advantages of this method can be carried out on a wide range of atmospheric detection and continuous monitoring. 
(5) by measuring the sub-sonic and other fluctuations in the atmosphere result of the interaction detection characteristics of these activities. For example, in the ionosphere in the role of the infrasound wave propagation interference by the road, you can determine the characteristics of infrasound, and further reveal the laws of ionospheric disturbances. 
(6) and other organisms can not only produce some of the reactions of sub-sonic, and he (or it) will have some faint organ infrasound. Therefore, the determination of these times can be used to understand the acoustic properties of the corresponding human organs or other biological activities.
4, animal infrasound can be issued:
Elephant infrasound issued their feet trample the ground, feet in the distance you can feel like the same kind;
Crocodiles in the water during the courtship back by vibration, infrasound issued, in the distance of the opposite sex can feel.
Tiger Tigers have the power of infrasound can shock the ears of joint dislocation of people, the sound from low to high, can spread very far.
Other whales, dolphins, manatees can feel thousands of miles away on the storm, earthquake, tsunami caused by infrasound.Ultrasound and infrasound contrast