Improvement using circular harmonics beamforming on reverberation problem of wave field reconstruction filtering

In real-time sound field transmission systems, the driving signals of a loudspeaker array should be obtained using only the received signals of a microphone array. For efficient transformation of signals of planar or linear arrays, we previously proposed a method of applying a transform filter in the spatio-temporal frequency domain; this filter is defined as the wave field reconstruction (WFR) filter. In linear array configurations, the major artifact of this method is an increase in reverberation time and a decrease in the direct-to-reverberant energy ratio (DRR) because reflections from above and below the microphone array can not be distinguished. We propose a method combining circular harmonics beamforming with the WFR filter as a preprocess in order to match the reproduced DRR to the original one at the time the direct sound wave is properly reproduced. Simulation results indicated that the DRR reproduced using the proposed method was much closer to that reproduced by the method without beamforming.