(1) Waveform and speed of sound of ultrasonic waves
Ultrasonic waves are mechanical waves that can propagate in gases, liquids and solids, in other words, ultrasonic waves can propagate in any medium with elastic properties. With the difference of the sound source, medium and boundary conditions, the wave patterns of the propagating ultrasonic waves are also different. waves, cylindrical waves, etc. Only a few of the most commonly encountered wave modes and sound velocities are described here.
① Longitudinal waves. When the ultrasonic wave propagates in the medium, the wave in which the vibration direction of the medium particle is parallel to the wave propagation direction is called the longitudinal wave. In the area where the longitudinal wave passes, the medium particles are periodically sparse and dense, as shown in Figure 2-3. Longitudinal waves can propagate in gaseous, liquid and solid media.