Last year, Ashley Jester came across an unusual old recording.
UNIDENTIFIED SCIENTIST: The date - 7 March 1949.
RASCOE: She's a researcher at the Woods Hole Oceanographic Institution in Massachusetts. The recording was part of a collection of plastic disks from a 1940s dictation machine at the institution's library. She was sorting through the scant notes with the disk left by scientists almost 80 years ago.
ASHLEY JESTER: And one of them jumped out to me immediately because it said fish noises. And I thought, that's probably not fish noises.
RASCOE: She eventually got it digitized and took a listen.
JESTER: As soon as I heard the recording...
JESTER: ...I thought it sounded like a humpback whale. I got excited and got goosebumps and then immediately started reaching out to my colleagues to say, is this really a whale?
PETER TYACK: So I only had to listen to a few tens of seconds, and the pattern of calls, the way it sequenced and the actual timbre of the calls is very distinctive with humpback whales.
RASCOE: That's Peter Tyack. He's a marine bioacoustician at Woods Hole.
TYACK: When the recording was made, nobody had a clue.
RASCOE: It turned out to be the earliest known recording of humpback whales by nearly 20 years and also of a quieter ocean.
TYACK: The oceans have changed a lot since 1949, so it was wonderful and emotional for me to hear this whale singing from so long ago. But it was equally exciting for me to hear what the ocean sounded like at that time. We have very few records of the ocean soundscape from such an early time period. It's very important because as we change the oceans, it changes the environment that animals have to communicate in.
RASCOE: For example, to be heard over shipping noise, right whales have been making their calls higher-pitched by about half an octave since 1950.
TYACK: So they've switched from being basses to being tenors in order to compensate for the low-frequency noise that's increasing.
RASCOE: The scientists in 1949 likely never knew what they recorded. They were in Bermuda testing how sound travels in the water. The recording was almost an afterthought, an engineer tinkering with new equipment, Jester says.
JESTER: And these were sounds that they couldn't explain, but they thought it was important enough not only to make notes of it, but to keep the recording going.
RASCOE: She says this scientific curiosity and basic research can help uncover the ocean's mysteries, even decades later.
RASCOE: That was Ashley Jester and Peter Tyack of Woods Hole Oceanographic Institution.
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