TDOA-Based Speed of Sound Estimation for Air Temperature and Room Geometry Inference

Spatially distributed acoustic sensors find increasingly many new applications in speech-based human-machine interfaces. One well researched topic is the localization of sound sources from Time Differences Of Arrival (TDOAs) measurements. Typically, the propagation speed of sound is considered a known constant. However due to temperature variations its value is known only up to some uncertainty. This paper exploits TDOA-based localization techniques in order to estimate accurately the actual speed of sound. Experimental results using both simulated and real data demonstrate the feasibility of the proposed method. Furthermore, the practical validation of this work considers two distinct experiments that are aimed at inferring information about enclosed sound fields. The first experiment concerns the calculation of the air temperature from the estimated speed of sound. The second experiment highlights the effects of temperature variations on the inference of the physical location of reflective boundaries of the acoustic enclosure. In the latter case it is shown that the position estimates of the reflective surfaces in a room can be improved when the correct propagation speed is first estimated using this method.