When a bubble reaches the surface, it ruptures with enough force to send a shockwave that sounds like cannon fire across the lake.
If that is their meaning, I will need more proof of the concept.
I don’t believe that a bubble breaking the surface would make such a loud noise.
No matter how large the bubble, there would not be enough pressure to create the sound.
I would imagine it’s similar to the noise that comes from a pot or boiling syrup. You hear a very light “plup” when the gas escapes. Obviously, in the 2 quart pan on my stove the sound is minimal. But there is a physical explanation. The surrounding liquid is displaced, and when the gas escapes into the air, the surrounding liquid rushes back to fill in the hole.
Now imagine that thousands of times larger. The sound would be loud and sharp.