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Spectral Frequency Tracker
(Forensics Version Only)
There are times when it is desirable to track a specific frequency as it varies over time in an audio file. The Diamond Cut Spectral Frequency Tracker, in conjunction with the Hi Definition Spectrogram provides for frequency tracking and creates an exportable file of the results for further examination (and comparison) via a spreadsheet program. An example where this is useful is involved with the authentication of a recording against the frequency vs time curve of the power grid in a certain locale. Details on this type of analysis can be found in and Application Note called “The Electric Network Frequency Analysis, AN-4” on the Diamond Cut Productions, Inc. website (www.diamondcut.com). Other applications for this function may involve plotting the RPM of an airplane engine based on the 400 Hz generator frequency variations found on a cockpit voice recorder following a forensics event (engines and generator speeds tend to decrease during a stall and speed up during a dive). Additionally, Doppler effects of sirens or bells on vehicles can be studied to help calculate vehicle velocity by exporting this data and analyzing it via a spreadsheet.
The frequency resolution of this system depends on your spectrogram FFT size and resolution settings. The Tracker allows you to choose the frequency window (Tracking Range – 0.01% to 100% of last scanned value) and the Samples (Samples to Average – up to 1000) over which the data is smoothed out. Using your mouse, simply point and click on the spectrogram to track a certain spectral line. When the “Filter Results” checkbox is checked, the data will be logged for direct visual inspection or for export. The data include Time, Frequency and Amplitude (in dB).
The Green line shows a non-constant Line Frequency
(located near the bottom of the display)
Spectral Frequency Data Ready for Export
The example above comes from a portable analog microcassette recording. Of note is the variation in the line frequency note or signal as shown by the green line on the Spectral Frequency Graph (which is overlaid upon the Spectrogram). This result is typical of a low cost battery operated analog tape recorder. These data can be dropped into a spreadsheet for further analysis and are in your choice of either .csv or .txt format. Click on the “Export” button to activate this feature.
Note 1: The Spectral Frequency Tracker responds to the channel selected. When both channels are selected, it responds to the sum of the two.
(Forensics Version Only)
There are times when it is desirable to track a specific frequency as it varies over time in an audio file. The Diamond Cut Spectral Frequency Tracker, in conjunction with the Hi Definition Spectrogram provides for frequency tracking and creates an exportable file of the results for further examination (and comparison) via a spreadsheet program. An example where this is useful is involved with the authentication of a recording against the frequency vs time curve of the power grid in a certain locale. Details on this type of analysis can be found in and Application Note called “The Electric Network Frequency Analysis, AN-4” on the Diamond Cut Productions, Inc. website (www.diamondcut.com). Other applications for this function may involve plotting the RPM of an airplane engine based on the 400 Hz generator frequency variations found on a cockpit voice recorder following a forensics event (engines and generator speeds tend to decrease during a stall and speed up during a dive). Additionally, Doppler effects of sirens or bells on vehicles can be studied to help calculate vehicle velocity by exporting this data and analyzing it via a spreadsheet.
The frequency resolution of this system depends on your spectrogram FFT size and resolution settings. The Tracker allows you to choose the frequency window (Tracking Range – 0.01% to 100% of last scanned value) and the Samples (Samples to Average – up to 1000) over which the data is smoothed out. Using your mouse, simply point and click on the spectrogram to track a certain spectral line. When the “Filter Results” checkbox is checked, the data will be logged for direct visual inspection or for export. The data include Time, Frequency and Amplitude (in dB).
The Green line shows a non-constant Line Frequency
(located near the bottom of the display)
Spectral Frequency Data Ready for Export
The example above comes from a portable analog microcassette recording. Of note is the variation in the line frequency note or signal as shown by the green line on the Spectral Frequency Graph (which is overlaid upon the Spectrogram). This result is typical of a low cost battery operated analog tape recorder. These data can be dropped into a spreadsheet for further analysis and are in your choice of either .csv or .txt format. Click on the “Export” button to activate this feature.
Note 1: The Spectral Frequency Tracker responds to the channel selected. When both channels are selected, it responds to the sum of the two.