According to studies made since 2009, the song of whales is becoming increasingly low.
Some assumptions tend to explain this sudden change, after millenia untouched. Noise pollution is oceans may be, for instance, part of the answer. The freighters and other boats produce a significatn noise. As water is an environment conductive to sound propagation, the noise of motors could have led the marine mammals to adapt, especially nearby the big sea routes.
Another assumption explains this key change with the increase in whales population. Since 1966 and the fishing ban, the species has repopulated its habitats, and the distance between individuals has reduced. To The Atlantic journal, whales “are maybe quieter today than in previous decades simply because they do not need to shout anymore”.
Another reason, even more alarming, is that the song of whales would not need to be so loud because of the increasing acidity of ocean waters linked with human activities. Indeed, sound waves propagate easily and further under these conditions.