Why is my can of soda making a buzzing sound?

Hi community!

First off, I'm sorry for posting here. It's not a super exciting topic but I couldn't ask on AskReddit because they didn't allow to use the text box and I have to give details.

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Something strange has happened that I've never experienced before. I was enjoying a can of soda when it began to make a buzzing sound that reminded me of a fly or some other type of bug. I also thought that it might be caused by the bubbles in the fluid popping at a set frequency and causing the buzzing sound, so to test my hypothesis I poured the liquid inside a clear glass, both to see if there was something alive floating in the liquid and to see if removing the source of the bubbles would also remove the buzzing sound.

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To my surprise, I completely emptied the can inside a clear glass and there was nothing strange inside the liquid. Furthermore, the can kept making the buzzing sound so it was clear it wasn't because of the CO2 being released by the liquid. Now I thought it was because there was an actual bug inside my can, so I cut the can in half.

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But I was surprised to see that the can was completely empty and clean, except for a couple of droplets of liquid left in it. I was even more surprised to hear that the can, which now I knew was completely empty, kept making the buzzing sound, with the same frequency as before. Nothing changed. There was no liquid, and no insect inside.

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The sound came from the top half, close to where the opening for the liquid to come out is. At least 30 minutes have passed and the can is still making those sounds. I have also discovered that I can cause the buzzing sound to be produced by the can by gently squeezing on it from one side.

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The only explanation I have left is that, since it is incredibly hot here (close to 37º C) and the liquid was cold, maybe the metal was contracting and dilating causing this squeaky, high pitched buzzing sound. Does anyone have a good explanation on why this could happen?