There are many types of digital evidence which could be encountered by digital forensic analyst in dealing with computer crime or computer-related crime. Not only files, videos, digital images, encrypted items, unallocated clusters, slacks and so forth, but also digital audio files might be analysed. In certain cases, the audio files become significant evidence to show the involvement of the perpetrators in the criminal case. Usually it contains speech records between two or more people talking about a plan to commit a crime; therefore the analyst should be able to reveal this conversation to the criminal investigators. With this evidence, the investigators have strong reason to prove that the perpetrators have planned a crime.
To reveal the conversation contained in the audio files is not an easy job. The analyst should follow strict guidelines of audio forensic so that the output of analysis could be accepted by the court. Once the analyst does one step of analysis carelessly, the results of analysis might be rejected by the court. To reach the results of audio forensic analysis in the best output, this journal discusses Standard Operating Procedure (SOP) of Audio Forensic. With this SOP, it is expected that the analyst could have a good guidelines in guiding them to perform audio forensic analysis in step by step, so that the result of analysis is reliable.
The SOP of Audio Forensic comprises five steps, namely acquisition, authentication, audio enhancement, decoding and voice recognition. Below is the explanation of each step.
To obtain the complete explanation of each steps above, please access this link http://www.scribd.com/doc/24292835/Forensic-Cop-Journal-2-2-2009-Standard-Operating-Procedure-of-Audio-Forensic to download the pdf version. Hopefully this journal could help digital forensic analysts to perform audio forensic analysis properly.