Abstract
The article presents the results of a part of research conducted by the authors into a wide range of work on automation of public safety systems. Their main purpose is to create, on the basis of sound signals analysis, system of warning against the use of firearms monitored public places not only at the time of shooting, but at the stage of preparing - the firearm reloading process. The range of acoustic measurements presented in the article and their analyzes included variability of sound emission of selected type of firearms depending on the number of operations and thus the degree of wear. Analysis of the recorded data will allow in the future to develop a system enabling not only to determine a type of firearm or tp narrow down the search area of individual specimens, but also to determine the degree of wear in terms of suitability for further use. The results discussed in the article correspond to two states of the same firearm model. The first is the initial state from the manufacturer’s factory after returning 50 control shots, the other after over 20,000 cycles. The used firearm was technically fully efficient, with no need to replace the elements during operation as well as tests. The presented scope of measurements includes spectral analysis of sound in the near field and time analysis of sound emission levels in the successive operation phases of the firearm mechanisms.
Highlights
Every working mechanical device emits sound waves regardless of its purpose
Sound waves with a pressure of up to 40 dB are perceived as quiet, above 60 dB they give the impression of increased loudness and values of 80 and more dB are treated as noise and can be harmful and in some cases even dangerous for our health
Two components of small-arms noise were distinguished: the muzzle blast and the sonic boom. In another approach aimed at a pattern recognition, shock wave, muzzle blast and reflections were distinguished, and gunshot signatures were divided into multiple classes [5]
Summary
Every working mechanical device emits sound waves regardless of its purpose. On their basis, people can make their classification, distinguish, determine location, etc. with the help of the sense of hearing This ability allows for recognizing the type of a working machine, and identification of a specific kind, which can be exemplified by a particular type of car from a group of motor vehicles. To analyze sound pressure levels generated by firearms with and without suppression devices, certified measuring devices are produced [6] Another problem solved with acoustic signal analysis is localization of a shooter. During our previous firearms studies, it was noticed that acoustic emission of the reloading process depends on the type of weapon [14], and on the quality of work and number of shots. This was the reason for starting research to determine the degree of wear of a particular type of weapon based on acoustic measurements. The main goal of the prepared system is automatic detection of reloading of weapon type and specimen before shooting and shooting in public places covered by audio-video surveillance (e.g. public offices, banks, museums, etc.) by means of sounds analisis
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