The Origin of Sonochemical Effects

The effects of ultrasound on chemical transformations are not the result of direct coupling of the sound field with the chemical species on a molecular level. Power ultrasound is able to produce 

FIGURE 2.28 Representations of sound motion. the ambient pressure in the fluid. (Reprinted from Mason, T. J., Sonochemistry, Oxford University Press, Oxford, 1999. With permission.) 

---

The origin of sonochemical effects in liquids is acoustic cavitation. Ultrasound is transmitted through a medium via pressure waves by inducing vibrational motions of molecules, which alternately compress and stretch the molecular structure of the medium due to a time-varying pressure. Molecules start to oscillate around their mean position, and provided that the strength of the acoustic field is sufficiently intense, cavities are created in liquids. This will happen if the negative pressure exceeds the local tensile strength of the liquid. 

---