Oof, sorry if that was misleading.

Maybe I'm overly fixated on the "to" in "to achieve": the whale doesn't care about the bubbles, they serve no important purpose in helping them sleep, it's just what happens when you vent air under water.

It's also kind of a nitpick, but the scientists refer to resting whales, but specifically state that they don't know if they are sleeping. I guess getting a proper EEG on a sperm whale is another scientific frontier.

Edit: An awesome scientific frontier: honestly if anyone deserves my tax money it's the grad student trying to figure out how to measure brain waves in a submerged oceanic whale.