Can you explain what these graphs are showing for me? I will readily admit that I have very little experience with analysis of audio data, but it looks like one recording is stereo data and the other is mono, and that the sample rates are also different. I'm not sure what differences I'm supposed to be looking at visually, but is it possible the differences you are seeing might be artefacts of the different recording parameters?
I apologize, I just realized I didn't answer your question xD.
Allright: In the Peak Frequency Graph (a sort of visual sound analysis) there is a very clear waveform (the one shown in the images I posted), that I have called the "Time shift wave". It is absolutely regular with very occassional breaks (I have not gone in detail about those breaks still). By comparing the same section of two different signals, I have found that the Time Shift Wave frequency was different. In other words, the second recording was "faster" than the first one.
This may mean that external factors may make the signal to change (IE, damage, presence of ships, materials, commodities, etc), or maybe that the signal has some sort of "evolution" that we have not yet found.
Hope this answers your question