The IceCube Neutrino Observatory will be upgraded with about 700 additional optical sensor modules and new calibration devices. Particularly, improved calibration will enhance IceCube’s physics capabilities both at low and high neutrino energies. An important ingredient for a good angular resolution of the observatory is a precise calibration of the positions of optical sensors. We present the concept of newly developed acoustic sensors that are mounted inside the optical modules and additional acoustic emitter modules that are attached to the strings. With this system we aim for the calibration of the detectors’ geometry with a precision of 10 cm by means of trilateration of the arrival times of acoustic signals. This new method will allow for an improved and complementary geometry calibration with respect to previously used methods based on optical flashers and drill logging data.