Sound Signal Separation Technique in Wind Tunnel Test by Using Planar Microphone Array

The traditional nearfield acoustic holography (NAH) requires free field on the side of the hologram plane back to the target sound source. There are often acoustic reflection and scattering caused by the interference source or the wall in the wind tunnel test, which greatly limits the application of NAH. By processing the sound signal measured by the planar microphone array, the target source and the interference source can be separated to achieve the purpose of indirectly removing the background interference. Aiming at the situation that the target sound source and the hologram are located inside and outside the wind tunnel jet respectively, combined with the convective wave equation solution in moving fluid medium and the classical shear layer correction theory, the spatial Fourier transform-based separation using single hologram is corrected. The target sound source inside the jet and the interference sound source outside the jet are separated, leading to the acoustic parameters of the target sound source acting on the hologram plane alone. Numerical simulations show that the change of working parameters has little effect on the separation results. The separation errors under different conditions are small, and the method has a certain anti-interference ability.