Nearfield acoustic holography in noisy environment based on the measurement using an acoustic mask with microphone array

Nearfield acoustic holography (NAH) has been widely used for identifying acoustic noise sources. However, conventional NAH is theoretically available only in the free field; therefore, the NAH may meet difficulties in many application in-situ environments. An NAH based on the measurement using an acoustic mask with microphone array is proposed in this presentation to reconstruct sound pressure and velocity of target sources in the environment with reflections and disturbing acoustic noise sources. The microphone array is flush-mounted at the bottom plane of an open rectangular mask. Four side surfaces are designed to acquire sound pressure in Neumann’s boundary condition. In an actual measurement, the mask faces to near field of a target source. Although the sound wave from disturbing sources may propagate into the mask by passing through the gap between the mask and source surface, the disturbing waves can be decomposed by the proposed NAH using inverse patch transfer functions. Numerical simulations and experiments indicate that this novel NAH using mask with microphone array is valid for reconstructing sound source in noisy environment. The influence of different distances between the source surface and the mask is also investigated.