We present a microphone array structure for spherical sound incidence angle tracking that can be attached to headphones or directly integrated into earphones. We show that this microphone array together with an ultrasonic sound source, e.g., a home assistant speaker in the room, allows to estimate the direction and distance of sound reflections on wall surfaces in the room. With our presented method, we achieved sound incidence angle estimation errors of around 14◦
in the horizontal plane and around 5◦ in the vertical plane, and reflection position estimation errors of around 5 cm within 2 m. Having the reflection points in 3D allows us to sparsely capture the closest room geometry at interactive rate, which is a necessary step towards indoor audio augmented reality applications.