Do you have any knowledge of ultrasound related technology?

Basic Introduction:

Ultrasound is a sound wave with a frequency higher than 20000 Hz, which is further divided into power ultrasound and detection ultrasound in practical applications. It has good directionality, strong penetration ability, and is easy to obtain concentrated sound energy. It can propagate over long distances in high-density solids and liquids, and can be used for ranging, industrial testing, medical ultrasound, cleaning, welding, drilling, gravel, sterilization and disinfection, etc.

Scientists refer to the number of vibrations per second as the frequency of sound, which is measured in hertz (Hz). The frequency of sound waves that can be heard by our human ears is between 20Hz and 20000Hz. When the vibration frequency of sound waves is less than 20Hz or greater than 20000Hz, we cannot hear them. Therefore, we refer to sound waves with frequencies above 20000 hertz as' ultrasonic waves'. The ultrasonic frequency commonly used for medical diagnosis ranges from 1 MHz to 10 MHz.

Theoretical research shows that under the same amplitude conditions, the energy of an object's vibration is directly proportional to the vibration frequency. When ultrasonic waves propagate in a medium, the frequency of particle vibration in the medium is very high, resulting in a large amount of energy. In the dry winter of northern China, if ultrasonic waves are introduced into a water tank, the intense vibration will cause the water in the tank to break into many small droplets. Then, a small fan can be used to blow the droplets into the room, which can increase indoor air humidity, This is the principle of ultrasonic humidifiers. For diseases such as pharyngitis and tracheitis, it is difficult to use blood flow to reach the affected area with medication. Using the principle of a humidifier to atomize the medication and allow the patient to inhale can improve the therapeutic effect. The enormous energy of ultrasound can also cause stones in the human body to undergo intense forced vibrations and shatter, thereby alleviating pain and achieving the goal of healing. Ultrasound is widely used in medicine, such as color ultrasound, B-ultrasound, and lithotripsy (such as gallstones, kidney stones, eye bags, etc.), which can also damage bacterial structures and disinfect items.

Generation method:

Sound waves are the form of propagation of mechanical vibration states (or energy) of objects. The so-called vibration refers to the round-trip motion of particles of a substance near their equilibrium position. For example, after the drum surface is struck, it vibrates up and down, and this vibration state propagates in all directions through the air medium, which is called sound wave. Ultrasound refers to a sound wave with a vibration frequency greater than 20000 Hz, and its frequency per second is very high, exceeding the general upper limit of human hearing (20000 Hz). People refer to this kind of invisible sound wave as ultrasound. Ultrasound and audible sound are essentially the same, and their common feature is a mechanical vibration mode that typically propagates in an elastic medium as a longitudinal wave, which is a form of energy propagation. The difference is that ultrasound has a high frequency, short wavelength, and good beam and directionality when  propagating along a straight line within a certain distance. Currently, the frequency range used for abdominal ultrasound imaging is between 2-5 MHz, Commonly used is 3~3.5 megahertz (1 vibration per second is 1Hz, 1 megahertz=10 ^ 6Hz, that is, 1 million vibrations per second, and the frequency of audible waves is between 16-20000 Hz).

The propagation laws of ultrasound in media, such as reflection, refraction, diffraction, and scattering, are not fundamentally different from those of audible sound waves. But the wavelength of ultrasound is very short, only a few centimeters, or even a few thousandths of a millimeter. Compared with audible sound waves, ultrasound has many strange characteristics: propagation characteristics - the wavelength of ultrasound is very short, and the size of typical obstacles is many times larger than that of ultrasound waves. Therefore, the diffraction ability of ultrasound is poor, and it can propagate in a straight direction in a uniform medium. The shorter the wavelength of ultrasound, the more significant this characteristic is. Power characteristics - When sound propagates in the air, it drives the particles in the air to vibrate back and forth, doing work on the particles. Sound power is a physical quantity that represents the speed at which sound waves do work. At the same intensity, the higher the frequency of a sound wave, the greater its power.

Due to the high frequency of ultrasound, its power is very high compared to ordinary sound waves. Cavitation - When ultrasonic waves propagate in a liquid, small cavities are created inside the liquid due to the intense vibration of liquid particles. These small cavities rapidly expand and close, causing violent collisions between liquid particles, resulting in pressures of thousands to tens of thousands of atmospheres. The intense interaction between particles can cause a sudden increase in the temperature of the liquid, providing a good stirring effect, thereby emulsifying two immiscible liquids (such as water and oil), accelerating the dissolution of solutes, and accelerating chemical reactions. The various effects caused by the action of ultrasound in liquids are called the cavitation effect of ultrasound.

Frequency above 2 × A sound wave of 10 kHz. The branch of acoustics that studies the generation, propagation, reception, and various ultrasonic effects and applications of ultrasound is called ultrasonics. The devices that generate ultrasonic waves include mechanical ultrasonic generators (such as gas whistles, sirens, and liquid whistles), electric ultrasonic generators made using the principles of electromagnetic induction and action, and electro-acoustic transducers made using the electrostrictive effect of piezoelectric crystals and the magnetostrictive effect of ferromagnetic materials.