Li Kai Ming, Lam Pou Man
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong.
J Acoust Soc Am. 2005 Jun;117(6):3716-26. doi: 10.1121/1.1904443.
It is known that the sound field in a long space is not diffuse, and that the classic theory of room acoustics is not applicable. A theoretical model is developed for the prediction of reverberation time and speech transmission index in rectangular long enclosures, such as corridors and train stations, where the acoustic quality is important for speech. The model is based on an image-source method, and both acoustically hard and impedance boundaries are investigated. An approximate analytical solution is used to predict the frequency response of the sound field. The reverberation time is determined from the decay curve which is computed by a reverse-time integration of the squared impulse response. The angle-dependence of reflection coefficients of the boundaries and the change of phase upon reflection are incorporated in this model. Due to the relatively long distance of sound propagation, the effect of atmospheric absorption is also considered. Measurements of reverberation time and speech transmission index taken from a real tunnel, a corridor, and a model tunnel are presented. The theoretical predictions are found to agree well with the experimental data. An application of the proposed model has been suggested.
众所周知，长空间中的声场并非扩散声场，经典的室内声学理论并不适用。针对矩形长封闭空间（如走廊和火车站）的混响时间和语音传输指数预测，开发了一种理论模型，在这些空间中，声学质量对语音很重要。该模型基于镜像源法，研究了声学硬边界和阻抗边界。使用近似解析解来预测声场的频率响应。混响时间由通过对平方脉冲响应进行逆时积分计算得到的衰减曲线确定。该模型考虑了边界反射系数的角度依赖性以及反射时的相位变化。由于声音传播距离相对较长，还考虑了大气吸收的影响。给出了从实际隧道、走廊和模型隧道测得的混响时间和语音传输指数。理论预测结果与实验数据吻合良好。还提出了该模型的一个应用。
