Direction measurement of airborne sound sources over a reflective ground using an array of virtual directional microphones

This study explores the use of a spherical array of four virtual directional microphones to find the direction of an airborne sound source. The bearing of the source is obtained by estimating the time difference of arrival of the sound signal between the directional microphone pairs. The challenge is to find the source direction when the array is located over a reflective ground. To address this, the directivity of the virtual directional microphones is adjusted to attenuate the amplitude of the ground reflections so that the target source direction can be obtained using simpler techniques based on a single source free field model. This work also evaluates the performance of the array for different aircraft type signals of one second length.