I watched the video, if you could make one from the front it would be good. I specifically hoped to see the pressure gauge (brew pressure) with the noise when you made a shot. This is because I noticed it didn't make the noise until probably the brew pressure peaked, and then stopped making the noise before the shot was finished, when I assume the brew pressure started to drop due to the increased permeability of the coffee puck.
I'm pretty sure it's noise from the expansion valve as I mentioned previously.