SonicBoom: Contact Localization Using Array of Microphones

In cluttered environments where visual sensors encounter heavy occlusion, such as in agricultural settings, tactile signals can provide crucial spatial information for the robot to locate rigid objects and maneuver around them. We introduce SonicBoom, a holistic hardware and learning pipeline that enables contact localization through an array of contact microphones. While conventional sound source localization methods effectively triangulate sources in air, localization through solid media with irregular geometry and structure presents challenges that are difficult to model analytically. We address this challenge through a feature-engineering and learning-based approach, autonomously collecting 18,000 robot interaction-sound pairs to learn a mapping between acoustic signals and collision locations on the robot end-effector link. By leveraging relative features between microphones, SonicBoom achieves localization errors of 0.43 cm for in-distribution interactions and maintains robust performance of 2.22 cm error even with novel objects and contact conditions – well below the maximum possible error of 36.6 cm for the given end-effector geometry. We demonstrate the system's practical utility through haptic mapping of occluded branch-like structures in a mock canopy setting, showing that acoustic-based sensing can enable reliable robot navigation in visually challenging environments.