.So those noises that we hear in the enemy boss rooms in Splatoon and the Octo Samurai's room i Splatoon 2, what is your personal theory on it. There are many popular theories as to what it can be but my personal theory aligns up mostly with the Octo Expansion theory. That being that the noises are coming from those who got to the so called "Promised Land."
The promised land in theory is what TarTar used to get people to find four parts if a giant blender and blend them into the sanitizing goo used to sanitize the octarians into TarTar's "perfect race." The noises are the last sounds heard of those who were blended to be a part of this project. While yes, we do hear mechanical sounds which could be the Octarian world falling apart, I think it's just he Blender shaking violently and eventually falling apart since we see that the blender not only has to be assembled, but also has to be used and then taken apart, seen in the scene where Agent 8 and Captain Cuttlefish are about to be blended in it. But who knows, we may never know or maybe we do and we don't have Nintendo to back us up on that. But like I said, what's your personal theory on it?