A Time Reversal-Based Acoustic Indoor Localization System at the Absolute Threshold of Hearing

We present in this paper an acoustic indoor location system that allows a simultaneous localization of sources with different location precisions. This is achieved by the use of the time reversal technique and the code-division multiple-access operation. The system was evaluated in terms of accuracy, precision, and location delay. Simulations and experiments were carried out while varying the number of sources and that of the precision levels. The effect of the signal-to-noise ratio on system performance was also studied. Results showed that our location system can achieve accuracy of 1.5 cm with 83% precision. Finally, we aimed to reduce the audibility of the location signal. An equalization filter based on the absolute threshold of hearing was applied to the emitted signal and a matched filter was introduced at the receiver. Results showed an improvement in location precision when compared with the location system without the equalization filter. A reduction in signal audibility was noted.