Liquids contains microscopic bubbles of size $10^{(-9)}$m to $10^{(-8)}$m. ultrasonic waves propagates longitudinally through liquids. The molecules of the medium moves back and forth in the direction of propagation of the wave. This movement induces alternate regions of compression and rare fraction. A decrease in pressure at the area of rarefaction causes local boiling of the liquid. This causes an intense evaporation in the bubbles and the bubbles grow in size. The growth of the bubbles leads to their collapse within a very short span of one millisecond. The collapse of numerous bubbles results into a large number of shockwaves due to which the local temperature increases by about $10^4$℃. The shock waves develop high crushing power of the liquid due to which the cavitation effect has applications like.

• Ultrasonic cleaning.
• Emulsification.
• Alloy formation.

This method is also called as agglomeration.