Safety Eng. Dept., Natl. Inst. for Resources and Environment, 16-3 Onogawa, Tsukuba 305, Japan
Underground spaces generally have complex networks of tunnels which include many intersections. When a disaster such as a fire and an earthquake breaks out there, correct transmission of sound information has an important role in order for people to evacuate from underground safely [Fujimiya and Miura, J. INCE Jpn. 6(5) (1982)]. From the above point of view, sound energy distribution characteristics at an intersection of a scale model tunnel were measured under several conditions. The scale model tunnel had a square cross section, and experiments were carried out under acoustically hard and soft conditions. Impulsive sound from an electrical sound source indicated high reproductivity and omnidirectional characteristics from a preliminary experiment in the anechoic room. In a case where the scale model tunnel has an orthogonal branch, it was observed that low-frequency components were mainly propagated toward the branch, and this tendency was changed according to the angle of intersection. Furthermore, qualitative numerical simulation on sound propagation in a tunnel with an intersection was developed and the results agreed well with experimental results.