Jacques Cousteau had it wrong. As anyone who’s dived within several miles of humpbacks can attest, Earth’s oceans are anything but a silent world. And while not much tops an underwater encounter with a whale, just hearing its eerie, mournful song is in itself an unforgettable experience for scuba divers.

And also an unexplained one. ­Despite decades of research, scientists still do not really know for sure why whales sing. However, several new studies on the ­subject have uncovered interesting findings, including:

Male humpbacks — the only gender that sings — might change their complex, repetitive patterns when another male is near, perhaps to size up a potential rival.

A study in the journal Royal ­Society Open Science compared the songs of whales off the east and west coasts of Africa. It demonstrated that the two ­populations interact with overlapping vocalizations. Younger and older males can sing completely different tunes, which also might change over time. “If I were swimming up with 15,000 whales and all the males were singing the same song, it would drive me crazy,” study author ­Melinda Rekdahl told The New York Times. It could be that “the females are just, like, ‘Give me a new song!’” Rekdahl said.

Humpbacks can abandon an ­elaborate song in favor of a simpler one. If the songs are intended to attract a mate, “it might be that a brand-new song is a bit sexier than continuing to sing the ­complicated version of the old song,” researcher ­Jenny Allen told the Times. “They’re simplifying it to make it easy to learn so much new material all at once.” Much like how rhymes in a rap song or ­poem can make it easier to remember, repeating patterns in whale song might serve the same purpose.

Certain blue and fin whale songs ­appear to be dropping in pitch, in recordings made from 2007 to 2016 in the ­southern Indian Ocean. Researchers speculate it might be because their populations are rebounding, and so the sound does not need to carry as far in order to be heard by another whale, or because ocean acidification is making sound carry farther.