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“Is it true?” one asks Hernandez as she tells them about the 528 hertz sound frequency her father asked her to play while he was dying in the hospital.

Previous research shows that "concert tremor" can be recorded as long-duration signals with narrowband, harmonic frequency peaks between 1 and 10 hertz.

In a study of mice, they found that daily exposure to light and sound with a frequency of 40 hertz protected brain cells from chemotherapy-induced damage.

It also operates at frequencies greater than 100 hertz, achieves displacements of 140% and can lift 22 times its body weight.

In contrast, the researchers involved in this work were looking for a collective hum at much lower frequencies — one-billionth of one hertz, far below the audible range — emanating from everywhere all at once.