When an alternating magnetic field is applied to a ferromagnetic material, then the rod is thrown into vibrations, thereby producing ultrasonic waves at resonance. Therefore ultrasonic waves can be produced using magnetostriction effect.

Piezo electric oscillators produce ultrasonic waves at resonance. That is when the frequency of the oscillatory circuit is equal to the frequency of the vibrating crystal.

When ultrasonic waves are passed through a liquid, the density varies layer by layer due to the variation in pressure and hence the liquid will act as a diffraction grating called acoustical grating.

When ultrasonic waves are passed through a liquid, due to variation in pressure, the liquid will act as diffraction grating called acoustical grating. Under this condition when a monochromatic light is passed through the acoustical grating, the light gets diffracted. By using this velocity can be determined.

Some materials cannot be welded at high temperature. In such cases, the welding can be done at room temperature using ultrasonics and is called cold welding.