Simulation Study On Low And Medium Frequency Sound Insulation Of Street Hollow Windows At Different Incident Vertical Angles

The existing health building evaluation is based on the sound insulation value of a single window in the diffuse sound field to predict the indoor sound pressure level.In fact,the sound insulation of the hollow window is different under different sound wave incident vertical angles.At present,there are few studies on the measurement and finite element simulation of the sound insulation effect of hollow windows at different incident vertical angles.The difference of indoor sound pressure level between diffusion sound field and different vertical angles also needs to be clarified.In the pursuit of high-quality building sound environment,it is necessary to carry out special research on the sound insulation of hollow windows at different vertical angles,explore the difference of sound insulation effect and analyze the influence mechanism of sound insulation effect.In this paper,a reference model of double-layer glass plate is established and its sound insula-tion effect is numerically simulated by finite element method,which is compared with the transfer matrix method and the previous sound insulation results.The results show that the’mass-air-mass’resonance frequencies of the finite element method and the transfer matrix method are consis-tent and consistent with the empirical formula calculation results when the sound wave is incident at a specific vertical angle.The sound insulation curves obtained by the two methods are also very close.The simulation values of sound insulation and weighted sound insulation in this paper fall within the range of predecessors.These all prove the reliability of the finite element method simulation and the rationality of parameter setting.In order to explore the influence of sound wave incident vertical angle on the sound insula-tion effect of hollow window,this paper establishes the same size glass plate and hollow window model,and numerically simulates its sound insulation under different sound wave incident ver-tical angles.The results show that no matter what the boundary conditions of the plate are,the smaller the incident vertical angle is,the larger the sound insulation and the low-medium fre-quency weighted sound insulation are.The trough of the sound insulation curve is mainly caused by physical phenomena such as’mass-air-mass’resonance,acoustic cavity modal resonance and natural frequency vibration of the plate.The displacement amplitude at the natural frequency of the sound insulation trough is much larger than that at the natural frequency without the trough,which is about 10～10³times.From the perspective of the vibration energy of the plate,the larger the incident vertical angle,the larger the mean square vibration velocity of the radiation plate,and the lower the sound insulation of the plate.When the incident vertical angle is 65°,the R_w+C_trof the two-glass-one-cavity window increases by 6 d B and 3 d B respectively when the plate thickness increases from 2 mm to twice.When the incident vertical angle is 25°,when the plate thickness is doubled from 2 mm twice,both R_wand C_trincrease by 5 d B.When the cavity thick-ness increases from 6 mm to 12 mm,the R_w+C_trof the two-glass-one-cavity window increases by 6 d B and 5 d B respectively when the incident angle is 65°and 25°.Regardless of the ver-tical angle,the improvement of the sound insulation effect of the hollow window is not obvious when the cavity thickness increases from 12 mm to 24 mm.Arranging sound-absorbing materials around the cavity can make the sound insulation curve smooth.The larger the incident vertical angle,the more obvious the effect of increasing the thickness and width of the sound absorbing material on the sound insulation effect.