Today ultrasound is applied in hospitals for medical imaging, in industry for welding plastics and cleaning
materials and even in the home for
burglar alarms and vaporizers. These
applications, however, do not utilize
the chemical effects of ultrasound. Ultrasound can increase the reactivity of
metal powders by more than 100,000
times. Ultrasound can drive metal particles together at such high speeds
that they melt at the point of collision,
and ultrasound can generate microscopic flames in cold liquids.