日韩欧美一二三,人妻一区二区高清免费,欧美 亚洲 日韩精品 一区,亚洲第一三级片网站

Industrial boiler fan noise pollution is mainly three factors, namely: sound source, the media and the receiver. Only the three exist at the same time in order to interfere with the listener. From the three aspects of the start, by reducing the sound source, limiting noise propagation, blocking the reception of noise and other means to achieve the purpose of noise control, in the specific noise control technology, can be used sound absorption, sound insulation and muffler three Measures.