Sometimes the past is sitting on a shelf, waiting to be heard. Researchers at Woods Hole Oceanographic Institution say a humpback whale song recorded in Bermuda in March 1949 is the oldest known preserved recording of its kind, and they say it could help scientists better understand how whales communicate.

The recording came from Woods Hole scientists working on a research vessel with the U.S. Office of Naval Research. They were testing sonar systems and carrying out acoustic experiments when they captured the sound, said Ashley Jester, director of research data and library services at Woods Hole in Falmouth, Massachusetts.

The scientists at the time did not know what they were hearing, Jester said, but they kept recording and saved the sound anyway.

“And they were curious. And so they kept this recorder running, and they even made time to make recordings where they weren’t making any noise from their ships on purpose just to hear as much as they could,” Jester told CBS News. “And they kept these recordings.”

Woods Hole scientists found the whale song last year while digitizing old audio recordings. Jester located the recording on a well-preserved disc made by a Gray Audograph, a dictation machine used in the 1940s.

“These audograph discs survived because of their material and careful preservation,” Jester said.

Peter Tyack, a marine bioacoustician and emeritus research scholar at Woods Hole, said the recording matters not only because it captured whale song, but because it also preserved the sound of the ocean around it.

“The recovered recordings not only allow us to follow whale sounds, but they also tell us what the ocean soundscape was like in the late 1940s,” Tyack said. “That’s very difficult to reconstruct otherwise.”

Tyack said the ocean of the late 1940s was much quieter than the ocean of today, giving scientists a very different background for whale song than the one they usually hear now.

He said a preserved recording from that period can also help researchers better understand how newer human-made sounds, including increased shipping noise, affect whale communication. Research published by the National Oceanic and Atmospheric Administration states that whales can vary their calling behaviour depending on noises in their environment.

According to Sean Hastings, a policy manager for NOAA, ship strikes and entanglements in fishing gear are currently the number one and number two threats to whales.

The recording also predates Roger Payne’s discovery of whale song by nearly 20 years.

Jester said the underwater recording equipment used in 1949 would be considered crude by today’s standards, but it was advanced for its time. She said the plastic disc is especially significant because most recordings from that era were made on tape, which has since deteriorated.

Whales rely on sound to survive. According to NOAA scientists, they make clicks, whistles and calls. Scientists say those sounds help them find food, locate each other, understand their surroundings and move through the ocean. Several species make repetitive sounds that resemble songs.

Humpback whales are among the best-known singers. They can weigh more than 55,000 pounds and are capable of complex vocalisations that can sound ethereal or mournful.

NOAA says humpback whales were listed as endangered in the United States in the 1970s, due primarily to commercial whaling, and a final moratorium on commercial whaling was established in 1985. NOAA says four of the 14 distinct population segments are still protected as endangered, and one is listed as threatened.

Tyack said underwater recordings remain an important way to study and protect whales.

“Underwater sound recordings are a powerful tool for understanding and protecting vulnerable whale populations,” he said. “By listening to the ocean, we can detect whales where they cannot easily be seen.”

Hansen Johnson, a research scientist at the Anderson Cabot Center for Ocean Life at the New England Aquarium who was not involved in the research, said the recording from a quieter ocean could help scientists better understand the sounds whales make today.

“And, you know, it’s just beautiful to listen to and has really inspired a lot of people to be curious about the ocean, and care about ocean life in general,” Johnson said. “It’s pretty special.”