Ultrasound Parameters

• Frequency: The number of times a vibrating particle goes through its original position within one second. The unit is “Hertz” or simplified as “Hz”. For ultrasound, the frequency is around mega hertz, or “MHz”.
• Propagation speed: The distance that the wave peak pass within one second. It is determined by elasticity and density property of the acoustic medium.
• Wave length: The distance between the two adjacent wave peaks
• Amplitude: For vibration, the amplitude is maximal distance a particle moves away from its original position.
• Pressure: Wave propagation can be  understood as the particles vibration abound their balance position, also can be think as pressure alternatively variation in the acoustic medium. Pressure, especially from the surface, cause particle to move. Take a small volume inside the acoustic medium, when more neighbor particles move in, a high pressure is introduced, and on the contrary, when the particle move out, a low pressure in generated.
• Power: Since the particles are vibrating, it possesses kinetic velocity and energy. An ultrasound source will generate energy, and this energy divided by time is power. When frequency is fixed, the power is proportional to the density and second power of particle vibration amplitude. When particles have the same vibration amplitude, the power will be proportional to the fourth power of the frequency.
• Intensity: it is the power on unit area.