1. Download the file “EvidenceFile.wav” and listen to it. Describe whether you can hear
hum from the fluorescent lights and whether you hear any gaps. If you suspect gaps, at
what time in the file do they occur? (0.5 points)
2. Use MATLAB and mesh/node analysis to plot the frequency response of the filter shown
in Figure 2. Your frequency axis should be linear and cover the range 10 to 110 Hz in 1 Hz
steps. Your vertical axis should cover from 0 to -40 dB. Determine the filter Q from your
plot using the center frequency/3 dB bandwidth formula. Include a listing of the
MATLAB code in the appendix of your report. (1 points)
3. Implement the filter from Figure 2 using LTSpice. Use AC analysis to plot the frequency
response. Include your schematic in your report. Your plot axes should be the same as in
the previous step. (1 points)
4. Feed your LTSpice circuit with the file “Evidence.wav.” Include a plot of the filter output
in your report. Comment on whether you see anything suggesting the audio has been
altered. Write the filter output to the file “Filtered Evidence.wav.” (2 points)
5. Use MATLAB and the properties of the Laplace transform to compute the frequency
response of the averaging FIR filter shown in Figure 3. Include a frequency response plot
in your report. Your frequency axis should be linear and cover the range 0 to 150 Hz in 1
Hz steps. Your vertical axis should cover from 0 to -40 dB. Observe your plot and
determine whether the filter will remove the undesired 120 Hz artifact from the
multiplier. (1.5 points)
6. Write a MATLAB script that accepts the file “FilteredEvidence.wav” and performs the
signal processing operations shown on the right of Figure 1. Include a listing of the
MATLAB code in the appendix of your report. (1 points)
7. Plot the output from the MATLAB script and include it in your report. (1 points)
8. Prepare a one-paragraph statement to the court indicating your expert opinion on
whether you believe the evidence is tainted and the basis for your conclusions. (1 points)
9. Your report should have a professional appearance and be created in Microsoft Word,
LaTeX, or a similar publishing program. You may include handwritten equations in an
appendix, but they must be properly referenced and clearly written. Equations in the
body of the report should be created with an equation editor such as the one included in
Word. (1.5 points)
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