New Forensics Demo Files
New Diamond Cut Productions DCForensics10.5 Demo Files
Three new demo audio files have been added to the Diamond Cut DCForensics10.5 software to help you understand some of it’s new features. Two of these files are simulations of real forensics audio situations that you may encounter while the last is taken from an old vertical cut acoustical recording. Here are the names of the new demo files and a description of each.
- Phase vs time Speech Demo
This file was made with a binaural (two-channel) microphone in a 36 foot long venue. The microphone was located on a stand at the half-way point (18 feet). Two people were located in the room, one at each end. The female voice remains physically stationary at the left side of the room, while the male (voice) slowly walks from the right side of the room and ends up on the left side of the room by the end of the recording (both persons being on the left side of the room by the end of the recording). The recording is of Lincoln’s Gettysburg address, with sections of the speech alternately being spoken by the male and female starting out with the male voice. If you bring up this file in classic edit mode and file sync mode and then click on the “View Channel Phase vs Time” feature (found at the bottom of the Forensics Menu), a green line will be displayed atop the spectrogram view. Note how the line has a slight positive slope (up and to the right) indicating the movement of the male voice in the room. Also, note that there are 4 edits points in the file, with two located amidst the speech portion. These are areas of interest of potential file tampering and need to be further explored via the software’s zoom function to evaluate what is going on at those positions.
- 60 Hz Phase Shift Demo
This file was created using the software. A 60 Hz, two channel signal was created using the Make Waves Generator (Edit Menu). It was then fed through the filter sweeper one channel at a time using the HP and LP functions set an octave away from the 60 Hz signal thus creating a variable phase shift of one 60 Hz signal compared to the other. This is intended to simulate an acoustical environment in which some 60 Hz acoustical noise is present in the venue (from things like HVAC systems, pumps, or large transformers) and is picked up by the stereo recorder. In practice, a pre-conditioning step would be included to low pass filter everything below 100 Hz so as to only allow the 60 Hz room noise to be recorded. Bring up this demo file along with the “View Channel Phase vs Time” feature. Note that a non-linear line is painted on the screen with discontinuities thereon. These discontinuities are areas of the file that have been modified and the edits are clearly shown in the phase vs time graph.
- Preamp Vertical Cut Demo
This demo file is a stereo recording of a vertical cut recording made around 110 years ago by Pathe’ (Skies of Normandy). If you try to play it in its raw state, the sound is overwhelmed by noise. However, if you bring up the Virtual Phono Preamp (VPP) and check the Mono and Verticals (L-R) check-boxes and then preview the file, it will become substantially clearer. The reason for this is because this combination of Virtual Phono Preamp check-boxes allows the system to resolve (decode) the vertical component of the recording while rejecting the lateral (or horizontal) component of the signal leaving behind a relatively clear signal. After this step has been performed on a vertical cut recording, use the normal steps you would use to remove the remaining impulse and continuous noises.