We have proposed a method called V2MA (VSVerb Virtual Microphone Array). This method virtually generates spatial room impulse responses (SRIRs) captured by a conventional microphone array using only a set of four impulse responses (IRs) measured by an A-format microphone in the target space. V2MA is based on the concept of geometrical acoustics, that involves a virtual sound source, also known as a mirror source. After measuring the four IRs using an A-format microphone, we calculate the instantaneous sound intensities in the x, y, and z directions. The “source intensities,” that contain sound source information, are detected from these sound intensities. Then, we estimate the locations, strengths, and phase characteristics of the sound sources. The spatial properties of the obtained virtual sound sources can be considered the fingerprint of a target space's reverberant characteristics. Using the manner of geometrical acoustics, we can update the spatial properties of the virtual sound sources to match a neighboring receiver position and a desired directivity. Lastly, we can obtain the SRIRs at any receiver (microphone) position with any directivity in the target room by translating the spatial information of the updated virtual sound sources into time responses. For immersive recording, large microphone arrays are often used. Using V2MA, we can virtually make an immersive recording using such a virtual microphone array, provided that we measure four IRs using an A-format microphone in the target space. In our previous study, we developed the framework of V2MA. To verify the plausibility of V2MA, this paper compares the responses of virtual (V2MA) and real (conventional) microphone arrays using measurement results collected in a practice IRCAM:Gallery under the various conditions. The results show similar overall characteristics, but also suggest the difficulty of a detailed evaluation. We also introduce practical examples of immersive recording using V2MA.
