In media forensics, the devices; e.g. computers, smart phones, still/video cameras, audio recorders, and software; e.g. video, audio, and graphics editors, file and disk utilities, mathematical computation applications, are, for the most part, black boxes. The design specifications are usually proprietary and the operating specifications may be incomplete, inaccurate, or unavailable. This makes it difficult to validate the technology, but using it without validation could discredit a practitioner's findings or testimony. The alternative is to test the device or program to determine relevant characteristics of its performance.
An important and common device in media forensics is the portable digital audio recorder used to record surveillance and interviews. This type can also be used to record the alternating current (AC) waveform from the mains power. While small variations in the AC frequency (ENF) can be forensically important, distortion in the recording can affect its value in adjudication or investigation. A method is presented to evaluate aspects of a recorder's operation that can cause distortion. Specifically, the method measures the noise generated by the recorder's electronics in its input and amplifier circuits. The method includes a procedure to isolate the recorder from environmental sources of noise. The method analyzes the broadband noise floor produced by the range of recording conditions and recorder settings. It also analyzes the noise amplitude for the harmonics for the mains frequency.
|Advisor:||Grigoras, Catalin, Smith, Jeff|
|Commitee:||Bregitzer, Lorne, Grigoras, Catalin, Smith, Jeff|
|School:||University of Colorado at Denver|
|School Location:||United States -- Colorado|
|Source:||MAI 53/01M(E), Masters Abstracts International|
|Subjects:||Electrical engineering, Computer science|
|Keywords:||Audio, Digital forensics, Media, Validation|
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