Acoustic Module for Direction Finding of Small Aircraft

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Introduction. The studied problem is relevant due to the growing use of unmanned small aircraft for mobile services of the mail and goods delivery, surveillance and security. At the same time, the danger of their use in events/campaigns, which pose a threat to both public and private interests, is increasing. Principally different devices are applied for surveillance; each type has its advantages and disadvantages. Passive acoustic surveillance tools provide stealth observation, but have a small detection range. It is possible to increase detection distance by improving the receiving microphones module design and developingeffective monitoring and localization algorithms. Theoretical Results. The paper presents the design of an acoustic module in the form of a tetrahedron with microphones located on its vertices. It is proposed to scan the space by angular coordinates using algorithms to generate a controlled power characteristic or controlled correlation characteristic. The theoretical justification of scanning algorithms, the results of the calculation of directivity characteristics and estimates of the error in determining the angular coordinates for each method are provided. Laboratory studies were conducted on direction finding of a noise source by the acoustic module prototype. Despite of reverberation in the room, it was possible to verify the theoretical results and confirm the advantage of the algorithm for the correlation formation of directivity. Conclusions. The results of the work can be used to create acoustic direction finders and systems for localizing noise objects. The proposed algorithm of controlled correlation characteristic can be used in monitoring tools to assess the acoustic characteristics of premises, for example, to experimentally determine the location and estimate sound absorption of enclosing constructions/the obstacles, to localize breaches in sound isolation.