Ultrasonic propagation concept

Ultrasound sounds like a very professional word. It was originally applied in medicine, and it was slowly applied in the industry. However, many people still don't understand the concept of ultrasound. We use our expertise to tell you about the concept of waves when studying the propagation process of vibration and the transmission process from sound source to receiver: The existence of the tribute is a necessary condition for transmitting sound waves.

For example, if a particle of the medium leaves the flat position, then the elastic force exerted by the other particles on it will force it to return to the original position. At this point, the adjacent particle itself leaves the equilibrium position again, and due to the inertial force, Even after the wave has passed, the medium will continue to vibrate near its original position. When the vibration frequency of the medium particle is in the human ear, the elastic wave we feel is the sound.

Ultrasonic waves can travel in any elastic object: liquids, solids and gases. At this time, the type of the wave is mainly determined by the elasticity of the medium. The liquid and gas do not have shear elasticity, so neither the ability to withstand any tangential stress nor any tangential stress. On the other hand, in two adjacent When the layer approaches and leaves, there will be a restoring force that hinders shearing and stretching. Just because the vibration of the medium particle is generated in the direction of the elastic restoring force, in liquids and gases, the wave can only be in the direction of wave propagation. Uniform particle propagation in the direction of vibration. This wave is called a paper wave. When the longitudinal wave propagates through the medium, it produces a continuous distribution of compressed and sparse fields. For example, standing waves, at the most amplitude point - the antinode - We will get the compressed region; correspondingly we will get the sparse region at the node. For traveling waves, at any point in space, it is alternately an antinode or a node.

The chopping waves in liquids and gases are determined by the fact that there is only one elastic coefficient in these media. When the deformation is around, the elastic force has the property of normal pressure, and the motion caused by it is perpendicular to the traveling wavefront. That is, in the direction of propagation. It has shape elasticity in solids, in addition to the normal stress generated by volume deformation, it also produces tangential shear stress. The deformation related to tangential stress propagates in the form of transverse wave. At this time, the medium particle The vibration is perpendicular to the direction of wave propagation. Therefore, in solids, helium can propagate longitudinal waves and can also transmit transverse waves. In pure transverse waves, the medium does not become dense and sparse. In solids, surface waves can be propagated.