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The clues are in the article. The tracks are called "Left Ear" and "Right Ear" and are on YouTube.
Search for "otoacoustic emissions" and you will find a bunch of research on this going back 30 years.
FWIW, the sound in the YouTube video sounds exactly like my tinnitus.
> Present in most children but believed to fade over time, they’re also found far more in musicians than in other adults, for reasons yet unknown.