Stable equalisation of ambisonic microphone arrays

Unprocessed microphone signals of ambisonic microphone arrays model acoustic scenes for higher orders insufficient and blurred. Thus, the contrast on the surface of ambisonic microphone arrays with digital gradient generation is insufficient and is not obtained naturally (acoustically). Therefore, it is necessary to process the microphone signals in order to generate the required signal differences for a spherical reproduction.The modal concept for incident sound fields and the corresponding radial steering filters describe the sharpening of acoustic scenes analytically.

Since these radial steering filters reach unfeasibly high magnitudes especially for low frequencies and for high relative distances between the analysis and synthesis radii it is necessary to limit their gain.

The equalisation of the physical microphone array itself can be seen as a pre-condition in order to apply the ideal modal concept and the corresponding radial steering filters. The adopted level of idealisation is thereby defined by measurements with the according microphone array.