Sound at frequencies above the audible range, i.e. above about 20 kHz.
Biological effects of ultrasound:
- Thermal – tissue is damaged due to heating
- Nonthermal – tissue damage due to mechanisms other than heating. These include mechanical forces on or within the tissue.
- Cavitational mechanisms – microstreaming, shock waves and microjets
- Non-cavitational mechanisms – radiation force, radiation torque and acoustic streaming