在线请人帮做个摘要英文翻译

Abstract: sound frequencies in more than 20000 Hz, the human ear can not hear the voice known as ultrasound. Since the 1940s, the rapid development of ultrasound technology, has become the face of new areas of expertise. When the vibration frequencies below 20 Hz, the people listen to a sound wave that is not the sound of it in the air, water, communication between the ground when the absorption barrier effect is very small, far distance, the penetration capability and its biological In effect and has caused damage of the current national attention to academics. In this paper, ultrasonic, sound and the emergence of communication mechanisms and the use of a detailed exposition. Besides a brief introduction of the noise generated and control theory.
Key words: ultrasonic sound waves, ultrasonic cavitation effects of noise decibels