城市隧道工程施工过程中产生的噪音会对附近居民造成严重的影响。由于超低频音的穿透力很强，隔音 门和隔音壁等常规消音措施无法有效消除超低频噪音的影响。针对 0~20 Hz 的超低频噪音，分析其在管道中的传 播规律和声波特性，发现：在管道中安设空心长管可以对超低频声波进行 2 次消音处理。第一次消音是利用入射 声波和反射声波相互干涉、抵消的原理，并根据管道声波的连续性条件使超低频声波在长管管口发生短路，阻碍 其继续向外传播；第二次消音是利用声波在变截面管道中传播发生能量衰减的原理，降低超低频噪音的能量。根 据该消音原理，设计出了一种可移动、抽拉式的超低频噪音消音装置，可有效消除隧道施工过程中产生的超低频 噪音。
During the construction of urban tunnel project, the noise generated by construction will have a serious impact on the nearby residents. Since the ultra-low frequency noise penetrating power is very strong, normal silencing measures can’t effectively eliminate the effects of ultra-low frequency noise. Aiming at ultra-low frequency tone for 0~20 Hz, the propagation law and acoustic characteristics of ultra-low frequency acoustic waves in a pipeline are analyzed. It is found that the hollow long tube in the pipeline can be used for twice to eliminate the ultra-low frequency sound wave. The first elimination of noise is the principle of mutual interference and cancellation by incident and reflected acoustic waves. Based on the continuity condition of the acoustic wave in the pipeline, the ultra-low frequency acoustic wave is shortly circuited at the nozzle of the long pipe. The second elimination of noise is the principle of energy attenuation, when sound waves travel through pipes of varying cross sections. According to the above theory, a movable and pumping type ultra-low frequency noise silencer is designed, which can effectively eliminate the ultra-low frequency noise produced during the tunnel construction.