Problems of Forensic Sciences 2019 Vol. 120 (CXX) 335-361
THE CHARACTERISTICS OF POPULAR AUDIO RECORDING APPLICATIONS INSTALLED ON SMARTPHONES WITH AN ANDROID OPERATING SYSTEM IN RELATION TO FORENSIC AUDIO ANALYSES
Marcin MICHAŁEK
Institute of Forensic Research, Kraków, Poland
Streszczenie
The number of evidence recordings made with devices such as smartphones has significantly increased in recent years. Dedicated applications are used for making recordings, which in Poland are installed mainly on the Android operating system. During the research, the properties of free audio recording applications that are most often downloaded from the Internet were examined. Ten different applications were selected and installed on modern smartphones, followed by making test recordings for further analysis. Despite the fact that the selected applications are rather simple, they all have considerable potential. Half of them have an option to edit their recordings. They also enable recording in various conditions and audio formats, such as: 3GP, AAC, AMR, M4A (MP4 with audio), MP3 and WAV, without or with signal compression. It was established that the data structure of these kinds of audio files contains a lot of valuable information that is useful for authenticity analyses, especially in the case of the MPEG multimedia container. This information helps to determine the device and the application used, the exact recording parameters and time when it was made and even whether it has been edited. Using the MATLAB computing environment, our own software was developed for the automatic analysis of the audio files structure in order to search for relevant metadata. The paper also describes the methodology of proceeding with the evidence smartphones and recordings, and, moreover, a way of safely copying data from their memory for further analysis. The obtained results have substantial value for examining the authenticity of audio recordings as part of forensic expert opinions. The acquired recordings also expand the constantly developed database of audio files, which is a useful tool for analyzing the authenticity of recordings.
Słowa kluczowe
Smartphone; Android recording application; Digital recording; Authenticity analysis; File structure.