欧美性XXXXX极品少妇_国产日韩亚洲欧美_欧美综合社区国产_欧美一级视频在线观看欧美

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.