Chiroform 125, Руководство пользователя

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Combination 860 50
Appendix A – Overview of treatment modalities
Ultrasound
Sound is a mechanical vibration. The human ear responds to these
vibrations in the range 20 Hz to 20 kHz. Sound above 20 kHz is called
ultrasound. Therapeutic ultrasound is sound in the range 500 kHz to 5
MHz.
Sound waves are produced by some disturbance in a material medium
causing the particles or molecules of the medium to vibrate. For this reason
sound will not pass through a vacuum. If the vibration is continuous and
regular a constant tone or frequency is produced. The vibration or sound
wave propagates through the medium as particles in the medium pass on
their vibration to neighbouring particles and a series of compressions and
rarefactions are produced in the direction of travel of the wave. Therefore,
sound waves are longitudinal waves.
The diagram shows a sound wave travelling from left to right. The vertical
bars represent thin slices of the medium which are displaced to form areas
of compression and rarefaction. The sine wave represents their
displacement relative to their mean position. The distance over which the
vibration repeats itself is called the wavelength. The number of complete
vibrations in one second is called the frequency of the sound wave.
The velocity of sound in the medium is given by:
Velocity = frequency x wavelength