Sound and Ultrasound Waves

In natural phenomena, in scientific experiment, and in technology, various forms of vibratory and wave motion are very often encountered. Among such movements are the well-known swinging of a clock pendulum, the vibration of a string, the movement of waves on the surface of water, the propagation of radio waves, and many others. Sound is also a wave motion. Sound waves arise and propagate not only in air and other gases but also in liquids and solids. To understand the properties of sound phenomena it is necessary to understand what vibrations and wave motion really are. It is therefore necessary to recall the basic properties and laws which characterize these two types of phenomena.