Spatial Subtraction of Reflections from Room Impulse Responses Measured with a Spherical Microphone Array

We propose a method for the decomposition of measured directional room impulse responses (DRIRs) into prominent reflections and a residual. The method comprises obtaining a fingerprint of the time-frequency signal that a given reflection carries, imposing this time-frequency fingerprint on a plane-wave prototype that exhibits the same propagation direction as the reflection, and finally subtracting this plane-wave prototype from the DRIR. Our main contributions are the formulation of the problem as a spatial subtraction as well as the incorporation of order truncation, spatial aliasing and regularization of the radial filters into the definition of the underlying beamforming problem. We demonstrate, based on simulated as well as measured array impulse responses, that our method increases the accuracy of the model of the reflection under test and consequently decreases the energy of the residual that remains in a measured DRIR after the spatial subtraction.