【作者】 王康；

【导师】 陶建成； 邱小军；

【作者基本信息】 南京大学 ， 声学， 2019， 硕士

【摘要】 建筑物中用于自然通风和采光的门窗等开口常成为室外噪声传入的主要路径。开口声传入控制方法包括开口结构设计、在开口中使用吸声材料等,但低频控制效果不明显。开口声传入的有源噪声控制分为两类,一是利用交错窗形成管道采用有源控制,二是直接在开口面上均匀布放有源控制系统。本文研究开口边界控制,即在开口边界上布放次级源来降低室外噪声的传入。首先,建立自由空间开口中声场理论模型,对自由空间中的开口声传输控制进行仿真,分析不同开口尺寸、次级源配置和入射角度对控制效果的影响,对开口边界控制的有效控制频率进行估计。结果表明开口边界控制的有效上限频率对应的波长和开口短边长相当。对于窄开口,开口边界布放的控制效果可优于均布开口的控制效果。其次,基于模态展开法,结合镜像原理和开口边界条件,建立无限大障板上一面开口的矩形箱内声场模型,采用边界元仿真验证该模型的正确性。对矩形箱开口声传入的有源控制进行仿真,分析不同次级源配置、矩形箱深度及初级源入射角度对有效控制频率的影响。结果表明正入射的边界控制性能较斜入射差,大角度入射时,边界控制效果的差异不明显。最后,针对矩形箱开口声传入开展实验,验证数值仿真的结果,分析不同入射角度对边界控制降噪量的影响,对比次级源布放在开口边界和开口面内的控制效果,分析仿真和实验误差的产生原因。全文研究的表明在开口边界上布放次级源来降低室外噪声的传入是可行的,其有效上限频率对应的波长和开口短边长相当。对于窄开口的有源声传入控制,开口边界布放可优于开口均布的效果。更多还原

【Abstract】 Openings in walls of enclosures or buildings can provide natural ventilation and light,which are often the weak link in the chain of sound insulation.The most often used method to reduce the noise is the passive noise control,including implementing special opening structures,inserting sound absorption materials and so on,which is not efficient for low frequency noise.For the active noise control,most of the systems are installed on the plenum windows or partially-opened windows,or have the secondary sources on the middle of the opening,leading to a limited ventilation.This paper investigates the feasibility of the boundary control system for sound transmission through an opening,which only installs the secondary sources on its frame.The main work is shown as follows:Firstly,an analytical model is provided to calculate the sound filed of an opening in free space.Simulations are carried out to discuss the effects of the size of the opening and the distribution of secondary sources on the effective control frequency(the lowest frequency when NR is less than 10dB)of the boundary control system.The results show that the effective control frequency of the boundary control system is decided by w with kw=2π where w is the length of the short sides of the opening and k is the wave number.The performance of the boundary control system can be greater than that of the surface control system when the number of secondary sources is limited or when the opening is narrow.Secondly,based on the modal expansion method,image method and the boundary conditions on the opening,an analytical model is developed to obtain the sound field transmitted into a cavity with a baffled opening,where the point source is outside the cavity.The analytical model is verified by the Boundary Element Method.Factors that affect the upper limit frequency are analyzed by different configurations of secondary sources and different depth of the cavity.It is also found that the control performance is lower for normal incidence and does not vary significant with large incident angles.Finally,the experiments are conducted to validate the theoretical model of the sound transmission through a baffled opening,and the effects of the incident angles are investigated.The performances of the boundary control and surface control are compared under broadband noise.The differences between the simulations and experiments are analyzed.The experimental results show that the control performance is lower for normal incidence and does not vary significant with large incident angles.The noise reductions of boundary control and surface control are similar when the number of secondary sources is limited.更多还原