The behavior of ultrasound is very similar to that of light waves and microwaves (radar), as they also exhibit properties such as reflection, refraction, interference, and propagation in a beam-like form. Higher frequencies enable ultrasound to be shaped into fairly well-collimated beams, and even sharply focused beams. Ultrasonic waves exhibit extremely strong reflectivity at the interfaces (surfaces) between different materials (technically referring to materials with significantly different acoustic impedances). The greater the difference in acoustic impedance between two materials, the higher the reflectivity at their interface.

Ultrasonic waves are almost completely reflected at the solid-gas interface (i.e., the solid-gas interface). The reflectivity of ultrasonic waves at the metal-air interface is extremely high, and even at the interface between two flat, polished metal surfaces pressed tightly together, there are still sufficient air molecules to produce strong reflection. Typically, the vast majority of energy in an ultrasonic beam is reflected from the solid-gas interface, while significantly less energy is reflected from molecularly bonded solid-solid interfaces (between different solids). Due to its beam-shaping capabilities, high reflectivity, and ability to penetrate optically opaque materials (such as metals), ultrasonic waves are highly suitable for measuring the dimensions of solid materials and inspecting their internal structures, requiring contact with only one surface of the material.