Scientists say they have worked out how the haunting songs sung by whales are produced.
The discovery shows that humpbacks and other baleen whales have evolved a specialised "voice box" that enables them to sing underwater, the BBC reported.
First published in the journal Nature, the discovery also revealed why the noise we make in the ocean is so disruptive for these ocean giants.
It was found that whale song is restricted to a narrow frequency that overlaps with the noise produced by ships.
"Sound is absolutely crucial for their survival, because it's the only way they can find each other to mate in the ocean," explained Prof Coen Elemans, of the University of Southern Denmark, who led the study.
"[These are some] of the most enigmatic animals that ever lived on the planet," he told BBC News. "They are amongst the biggest animals, they're smart and they're highly social."
Baleen whales are some of the world's largest animals. They are a group of 14 species, including the blue, humpback, right, minke and gray whale. Instead of teeth, the animals have plates of what is called baleen, through which they sieve huge mouthfuls of tiny creatures from the water.
To get their findings, they carried out experiments using larynxes, or "voice boxes", that had been carefully removed from three carcasses of stranded whales - a minke, a humpback and a sei whale. They then blew air through the massive structures to produce the sound.
In humans, our voices come from vibrations when air passes over structures called vocal folds in our throat. Baleen whales, instead, have a large U-shaped structure with a cushion of fat at the top of the larynx.
This vocal anatomy allows the animals to sing by recycling air, and it prevents water from being inhaled.
The researchers produced versions of the sounds using computers which showed that baleen whale song is restricted to a narrow frequency which overlaps with noise produced by shipping vessels.
"They cannot simply choose to, for example, sing higher to avoid the noise we make in the ocean," explained Prof Elemans.
His study demonstrated how our ocean noise could prevent whales from communicating over long distances, knowledge that could be vital for the conservation of humpbacks, blue whales and other endangered giants of the sea.
Whale communication expert Dr Kate Stafford, from Oregon State University, described the study as "groundbreaking".
"The production and reception of sound is the most important sense for marine mammals, so any studies that elucidate how they make sounds has the potential to move the field forward," she said.
Dr Ellen Garland, from the Sea Mammal Research Unit at the University of St Andrews, said: "I've always wondered exactly how baleen whales - especially humpbacks, which my research is focused on - actually produce the variety of sounds they do.
"Studying large whales is extremely challenging at the best of times, but trying to uncover how they produce sound when you may not even be able to see them underwater while vocalising is an added level of difficulty, so these researchers have been very creative."
