Sonication is act of applying sound (usually ultrasound) energy to agitate particles in a sample, for various purposes. In the laboratory, it is usually applied using a ultrasonic bath or an ultrasonic probe. In a paper machine an ultrasonic foil can distribute cellulose fibres more uniformly and make the paper stronger.
Sonication can be used to speed dissolution, by breaking intermolecular bonds. It is especially useful when it is not possible to stir the sample, as with NMR tubes. It may also be used to provide the energy for certain chemical reactions to proceed. Sonication can be used to remove dissolved gases from liquids (degassing) by sonicating the liquid while it is under a vacuum. This is an alternative to the freeze-pump-thaw and sparging methods.
In biological applications, sonication may be sufficient to disrupt or deactivate a biological material. For example, sonication is often used to disrupt cell membranes and release cellular contents.
Sonication can also loosen particles adhering to the wall of a vessel. Therefore it can be used as a cleaning step, easier than scraping them off with a spatula. Outside the field of laboratory science, sonicating baths are used to clean objects such as spectacles and jewelry.