  In this paper, we present an acoustic localization system for multiple
devices. In contrast to systems which localise a device relative to one or
several anchor points, we focus on the joint localisation of several devices
relative to each other. We present a prototype of our system on off-the-shelf
smartphones. No user interaction is required, the phones emit acoustic pulses
according to a precomputed schedule. Using the elapsed time between two times
of arrivals (ETOA) method with sample counting, distances between the devices
are estimated. These, possibly incomplete, distances are the input to an
efficient and robust multi-dimensional scaling algorithm returning a position
for each phone. We evaluated our system in real-world scenarios, achieving
error margins of 15 cm in an office environment.
