屋顶振源室内低频耦合响应场有限元研究

Low frequency coupled interior sound fields due to vibrating sources on roof

利用有限元方法计算了低频激发力作用下屋顶振源在室内产生振动耦合响应场的空间分布及其频率响应特征;指出了薄壁矩形封闭空间与刚性壁空间的模态频率存在一定偏差,并且在模态频率较高时偏差比较大.在激发力频率接近房间结构的共振频率或腔内声模态频率时,室内耦合声场将获得较大声压级,特别是当结构共振频率与腔内模态频率发生重叠时,以该频率激发结构会使室内耦合响应场的声压级得到极大加强,因此,在设计建筑物时应当避免共振频率与模态频率的重叠.通过分别计算在非特征(共振或模态)频率(80 Hz)与特征(共振和模态重叠)频率(116 Hz)激发力作用下的各壁声压级及其结构位移振幅分布,给出了各壁面在相应激发力作用下向室内辐射声能量的相对贡献,指出对室内声能量贡献起主要作用的有时不一定是屋顶,而可能是侧面墙壁.

The coupled interior sound fields and its frequency response due to vibrating sources of low frequencies on the roof have been calculated by using of finite element method (FEM). The results show that there are some differences of mode frequencies between thin-walled and rigid walled of the same dimension rectangular rooms, and it is found that the difference will be larger since the mode frequency is larger. If the exciting forces frequency is near by the resonance frequency of room structure or the sound mode frequency of the room, the pressure level of coupled interior sound fields will be enhanced. When the structure resonance frequency is equal to the room's mode frequency, the sound pressure level in the room will become very high at this exciting frequency. So this case must be avoided in the engineering. The sound pressure level and the displacement on the all walls are separately calculated at the characteristic and non-characteristic frequency (80 Hz and 116 Hz). It reveals that the mostly sound energy radiated to the room is not always contributed by the roof, sometimes the other walls may be the mostly one.