How to calculate the ultrasonic frequency? The sound velocity in solids is also different. After repeated measurement, it is found that sound waves propagate in solids in the form of longitudinal waves and transverse waves, and the wave velocities of these two waves are also different. For example, in stainless steel, the longitudinal wave velocity is 5790 M / s and the shear wave velocity is 3100 M / s. The stainless steel is made into a rod, and the longitudinal wave velocity in the rod is 5000 meters / second. In metals, beryllium is an expert in sound transmission. In rods made of beryllium, the longitudinal wave velocity of sound waves reaches 12890 meters / second, 38 times that of atmospheric sound. Polyethylene plastic has poor sound transmission ability. The longitudinal wave velocity in polyethylene rod is only 920 M / s, which is not as fast as the sound velocity in water. The soft rubber is elastic, and the sound wave cannot move inside. The speed is only 30-50 meters / second, which is not as fast as the sound speed in the air! Wave speed divided by frequency equals wavelength.
Ultrasonic wave is a sound wave with a frequency higher than 20000 Hz. It has good directivity, strong penetration ability, easy to obtain concentrated sound energy, and has a long propagation distance in water. It can be used for ranging, speed measurement, ultrasonic cleaning machine, welding, gravel, sterilization, etc. It has many applications in medicine, military, industry and agriculture. Ultrasound gets its name because its lower frequency limit is about equal to the upper limit of human hearing.