超声波的产生----外文翻译.doc

附录3 外文复印件 Ultrasonic wave production: The sound wave is the object mechanical vibrations condition (or energy) dissemination form. The so-called vibration is refers to material the particle the reciprocating motion which carries on nearby its position of equilibrium. For example, drum surface after rap, it on high and low vibrates, this kind of vibrational state to disseminates in all directions through the air medium, this is a sound wave. The ultrasonic wave is refers to the vibrational frequency to be bigger than above 20KHz, its each second vibration number of times (frequency) very high, has surpassed the person ear sense of hearing upper limit (20000Hz), people sound wave named ultrasonic wave which cannot hear this kind. Supersonic and may Wen Sheng be essentially consistent, their common ground is one kind of mechanical vibrations, usually will disseminate by the longitudinal wave way in the elastic medium, will be one kind of energy dissemination form, its diversity will be the ultrasonic frequency is high, the wave length, will have the good beam in certain distance along the straight line dissemination and the directivity, at present the abdomen supersonic image formation will use the frequency range in 2~5MHz, (will vibrate 1 time for 3~3.5MHz each second is 1Hz,1MHz=106Hz commonly used, namely each second will vibrate 1,000,000 times, but Wen Bo frequency between 16-20000HZ). Two main parameters about ultrasonic wave: Two main parameters about ultrasonic wave are: Frequency: F≥20KHz; Power density: p= emissive power (W)/emitting area (cm2); Usually p≥0.3w/cm2; The supersonic wave energy which disseminates in the liquid carries on the clean to the object surfaces contamination, its principle available “the cavitation” the phenomenon explained: The ultrasonic wave vibration disseminates when the liquid the sound wave intensity of pressure which achieves an atmospheric pressure, its power density is 0.35w/cm2, by now the ultrasonic wave sound wave intens