Question

how is ultra sound used for clearning

Answer 1

the object to be cleaned is placed in a cleaning solution an dultrasound waves was passing into the solution due to theur high frequency,the ultrasound stir up  the clening solution because of stirring the particle of dust sticking to the dirty object vibrate too much ,become loose, get detached from objrct and fall into solution the object cleaned throughly

Answer 2

Ultra sound is used to clean the dirt of small metals or jewellery by producing high frequency.. 
When high frequency of sound waves is produced they.. displaces the dirt by large movement of particles. The small metal is dipped in Washing Liquid ...where removing of dirt by Ultra Sound.. works..