Identification of firearm calibers via acoustical signature of the ejected cartridge case

Audio gunshot recordings can be very helpful for crime scene investigation although there are several technical challenges for the forensic experts to extract useful information. In this paper, we focus on a specific mechanical action of the firearms: the ejection of used cartridges. First we propose an acoustical model to the cartridge cases inspired by acoustical physics concepts. In the sequence we validate our proposed model using controlled measurements from four different calibers. In addition, by taking 339 gunshot recordings from YouTube, we show that our proposed scheme can identify the firearm calibers in 75% of the cases.