Mechanical oscillations, ultrasound

Mechanical oscillations of >18,000 Hz are referred to as ultrasound. In solid bodies, sound waves spread longitudinally as well as transversally in fluids, gases or body tissue, however, waves only spread longitudinally. The average velocity of sound conduction (v) in tissues is approximately 1,500 m/sec. 

Ultrasonic welding uses high-frequency ultrasonic acoustic vibrations to bond surfaces together. The ultrasonic frequency is commonly in the range of 20-40 kHz. The ultrasound is generated by an ultrasonic generator, and a piezoelectric converter transforms the ultrasound frequency into a mechanical oscillation. The booster-sonotrode unit intensifies the oscillation up to amplitudes of 10-20 pm. This amplitude of the horizontal oscillation is coupled... 

Ultrasound (or sonophoresis) is a technology more traditionally associated with the fields of physiotherapy, sports medicine, and medical imaging rather than transdermal dmg delivery. Compared to physiotherapy, where high-frequency energy (1 MHz) is used, in transdermal dmg delivery low-frequency energy (20 kHz region) is applied across the skin. Cavitation, the acoustically induced formation and oscillation of gas bubbles formed because of the mechanical energy supplied, is the most probable... 

The piezoelectric effect is another significant property of BaTiOj and oil ferrcelectrics. A change in the dimension of crystals is caused by the influence of electrical field and vice versa potential difference develops on the crystal surfat under the effect of an external mechanical stress. The phenomenon is made use in microphones, loudspeakers, oscillators for ultrasound generation, resonators frequency control, etc. 

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