Study on time synchronization in wide-area, multi-point sound measurements without the use of extension cables

Wide-area, multi-point sound measurements are conducted to investigate the propagation and localization of noise generated by various sources, including transportation and industrial activities. Sound level meters are typically used for such measurements. To capture sound propagating at approximately 340 m/s as a simultaneous event across multiple locations, traditional systems have used cable extensions connected to multi-channel recorders for synchronization. With recent advances in network technologies, it has become practical to configure systems in which sound level meters function as edge sensors. By combining sound level meters with small computers such as the Raspberry Pi, each device's internal clock is corrected using GPS or NTP signals to achieve synchronization across multiple units. The accuracy of synchronization was evaluated by applying cross-correlation functions to the measurement data, and the results were compared with those obtained from conventional cable-based synchronization. According to the best trial data, synchronization within approximately 10 ms was obtained without the use of cables.