# Acoustic Localization for a Moving Source Based on Cross Array Azimuth
## 1 Introduction  
The localization of moving sources represents a major issue in engineering applications. Similar to other detection technologies, acoustic-localization methods have been developed rapidly over the years. Meanwhile, the noise generated by low-speed vehicles (LPVs) is a key issue, especially in connection with acoustics mitigation, where noise pollution continues to be a major health problem, with a whole host of health effects, such as: sleep disorders with awakenings [1], learning impairment [2; 3], hypertension ischemic heart disease [4], and especially annoyance [5], a widely used indicator to study the effect of different noise sources on wellbeing. In this context, the main effort has been done to mitigate the main sources of noise: road traffic [6; 7; 8], railway traffic [9; 10], airport [11; 12], and industrial [13]. Specifically about road noise, the most important interaction producing noise, more than just the engine noise used for the LPV, was also road/tire interaction [14; 15] and aerodynamic noise for high-speed vehicles. Furthermore, a relatively new noise source is impacting modern society in areas where background noise is low. Wind farms are being installed continuously every year to supply energy demand, but people are being affected by its noise, which is more disturbing than other sources [16; 17] and the scientific community is moving towards its assessment [18].  
In this paper, the LPV is the research object. As for all moving vehicles, exhaust systems and chain tracks are the main noise sources of LPVs, with exhaust systems representing the dominant factor. Therefore, exhaust systems could be chosen as the moving noise source. The most commonlocalization methods for noise sources are Nearfield Acoustic Holography (NAH), beamforming, and array signal processing [19]. The sound field of a moving vehicle is effectively measured based on NAH with a moving acoustic plane [20] and coordinate compensation [21; 22]. Far-field measurements of a moving source can be achieved by the short-time beamforming method, but these require extensive computational resources for processing the acquired data for the acoustic plane frame at every moment. The false noise source (ghost image) would also be easily generated [23; 24]. For array signal processing, the required computations are fast and can be performed to high precision [25; 26]. This is so since the necessary calculations to be performed on the signals are only one-dimensional and, therefore, substantially less demanding than those for a whole acoustic plane.  
The localization method of a moving sound source for the new method described here is achieved by intersecting the azimuth lines of cross arrays. Initial testing of the localization algorithm and the data analysis were performed for a single array and revealed a good performance. Therefore, a second array was added to cross the azimuth lines. The locating experiments were conducted with the engine noise of an LPV as a moving noise source. The data length determined by short-time correlation and path compensation were also introduced. The new method succeeded in effective localization of moving vehicles, requiring less expensive instrumentation than existing methods. Moreover, it was found that it continues to perform properly even under adverse ambient conditions, such as bad weather or at low light levels at night.