航空声学风洞3/4开口试验平台地板对远场噪声测量的影响

利用Kirchhoff-Helmholtz声学理论建立了地板声波反射问题的时域理论模型，推导了地板面上反射波的幅值函数和延迟时间的表达式，并引入了恰当的数值方法对反射声场进行求解，理论方法的正确性得到了实验结果的验证。以典型的高斯调制正弦波脉冲和连续正弦波为例，用建立的理论方法对噪声信号的传播过程和平台地板对远场噪声测量的影响进行了数值模拟研究，结果表明：地板的存在将使得远场接收到的噪声信号中出现直达波和反射波，反射波包含了中心波和边缘波。在低频段，地板宽度增加，远场噪声声压级增大；在高频段，地板宽度增加对远场总噪声级影响不明显。对于高速列车（HST）模型，车底位置的声源比车顶位置的声源在高频段受到地板反射的影响更大。

Influence of a 3/4 open jet floor on far field noise measurements in aeroacoustic wind tunnel

Based on the Kirchhoff-Helmholtz diffraction theory, a transient theoretical model for the reflection of spherical sound wave from a 3/4 open jet floor is built, and the amplitude shading and time delay function for the reflection sound pressure on the floor is derived. A numerical method is introduced to solve the reflection sound field. The correctness of the presented method is verified by an experiment. In this study, sin-burst pulse and continuous sinusoidal wave are used to study the propagation of the sound wave and the influence of the 3/4 open jet floor on the far field noise measurements, respectively, and the following results are obtained:the received sound signal contains the directed wave and reflection wave, and the reflection wave is further divided into the center wave and edge wave. In the low frequency range, when the floor width increases, the far field sound pressure level increases accordingly, while in the high frequency range, increasing the floor width has non-obvious effect on the far field noise level. For a high speed train (HST) model, the bogie noise source is easier to be influenced by the floor than the pantograph noise source.