1. Is the x axis in Hz?
I believe so, because hertz is defined as cycles per second. I considered 1 cycle to be every 1 time we read the pressure map and this happens every 13ms (0.013 seconds) and so I think the frequency is indeed measured by Hz in all the plots.
2. How many samples are used in each FFT?
We collect 2000 samples of the pressure map before plotting them so the number of samples for each FFT plot is 2000.
3. Confirming that the amplitudes are on the same numerical scale?
I fixed the scale for all the amplitudes. The resulting FFT plots are a lot more reasonable and I believe beautiful. They are all shown below.
4. What are the spikes at 7-8 Hz and 16 Hz?
A spike at 7 Hz means every 0.142 seconds a sudden pressure is read, which is equal to every 10.9 samples. Considering something happens once in every 10 samples, we would have that spike at 7.69 Hz which matches the observations of the spike between 7-8 Hz.
In addition, if a sudden noise happens once in every 5 samples, we should see a spike at 15.38 Hz which is again matching the observations.
5. Are those two blank cells really dead, or are they just incredibly clean?
Truth is, there are actually 4 cells that have flat lines. These 4 cells are at locations (1,9), (1,10), (2,9), (2,10). These locations correspond to the very black spot at the corner of the pressure map and I would say it is not clean at all.
6. Why is there so much variability in noise levels among the cells?
Fixed Power Scale FFT plots:
(1,1):
(1,2):
(1,3):
(1,4):
(1,5):
(1,6):
(1,7):
(1,8):
(1,9):
(1,10):
(2,1):
(2,2):
(2,3):
(2,4):
(2,5):
(2,6):
(2,7):
(2,8):
(2,9):
(2,10):
(3,1):
(3,2):
(3,3):
(3,4):
(3,5):
(3,6):
(3,7):
(3,8):
(3,9):
(3,10):
(4,1):
(4,2):
(4,3):
(4,4):
(4,5):
(4,6):
(4,7):
(4,8):
(4,9):
(4,10):
(5,1):
(5,2):
(5,3):
(5,4):
(5,5):
(5,6):
(5,7):
(5,8):
(5,9):
(5,10):
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