Isotropic noise modelling for nearfield array processing

An exact series representation for a nearfield spherically isotropic noise model is introduced. The methodology uses the spherical harmonics expansion of the wavefield at a sensor to obtain the correlation between two sensors due to the nearfield isotropic noise field. The result is useful in nearfield application of sensor arrays. The proposed noise model can be utilized effectively to apply well established farfield array processing algorithms for nearfield applications. Specifically, any signal processing criterion based on farfield isotropic noise correlation can be reformulated with nearfield noise with this representation. A simple array gain optimization is used to demonstrate the new noise model.