空场及有车状态下隧道混响特性预测分析

Analysis of Tunnel Reverberation Characteristics in Empty Filed and Vehicle Conditions

隧道混响是隧道内列车噪声显著的关键因素,对混响特性进行预测分析有助于隧道内的降噪研究。采用脉冲响应积分法测试空场隧道混响时间,利用虚源法建立隧道壁面吸声系数数值计算模型,反推隧道壁面的吸声系数,将其输入给基于声线跟踪原理建立的隧道内声场响应预测分析模型,以混响时间和D/R比(Direct/Reverberant ratio)详细分析隧道内车体表面声场的混响特性。结果表明:隧道壁面吸声系数经验值与反推计算结果有较大差异,低于400 Hz频段经验值高于计算值,而高于400 Hz频段则反之。在车底响应面声源中心区域内直达声场强于混响声场,车底响应面的混响声场强度高于车顶响应面。混响时间均匀度从高到低的响应面分别为:车底、车顶、侧面,空场状态响应面上的平均混响时间明显高于有车状态下,其中车底响应面的最低。

Tunnel reverberation is the key influence factor of significant train noise inside the tunnel,analysis of reverberation characteristics is helpful to the research of noise reduction in tunnel.The reverberation time of tunnel in empty field condition was measured by integrated impulse response method.The numerical calculation model of sound absorption coefficient of tunnel wall was established by image source method.And the sound absorption coefficient of tunnel wall was deduced.The sound absorption coefficient was input to the prediction model,which was established based on the ray tracing method,to predict the sound field response in the tunnel.And the reverberation characteristics of the sound field on the surface of vehicle body in tunnel were analyzed according to reverberation time and Direct/Reverberant ratio.The results show that the empirical value of sound absorption coefficient of the tunnel wall is quite different from the calculated result.In the frequency band below 400 Hz,the empirical value is higher than the calculated value,while in the frequency band above 400 Hz,the empirical value is lower than the calculated value.In the central area of the bottom response surface,the direct sound field is stronger than the reverberant sound field,and the intensity of the reverberant sound field on the bottom response surface is higher than that in the top response surface.The response surfaces with the uniformity of reverberation time in the order from high to low are bottom,top and side.The average reverberation time on the response surface of the empty field state is significantly higher than that of the vehicle state,and the response surface of the vehicle bottom is the lowest.