After analyzing similar recordings, the Cuban government had also pointed its finger at crickets. But they blamed the wrong species—one whose song sounds very different, even to untrained ears. By contrast, the song of the Indies short-tailed cricket matches the Cuban noise in several telltale ways. Both are loudest at a frequency of 7 kilohertz, roughly an octave beyond the highest notes on a piano. Both consist of pulses that repeat 180 times a second. In both, each pulse consists of 30 oscillations, which become slightly lower in pitch as they die away.

Read: The case of the sick Americans in Cuba gets stranger

Only one thing didn’t match: The pulses in the AP recording were more erratic and variable than those of most insects. But that, Stubbs thinks, is because the cricket’s call was probably echoing off the surfaces of an indoor space, creating several sound streams that interfered with one another. When he played and recorded the cricket’s call indoors, the result matched the Cuban noise even more closely.

Cricket behavior could also help explain another mysterious detail of the Cuban incidents: Several diplomats claimed that the sound abruptly stopped when they entered a room or moved around. That’s “consistent with an insect stopping a call when threatened,” Stubbs and Montealegre-Z write.

Of course, the diplomats could have been attacked in some other way. Or their symptoms might be the result of a mass psychosomatic illness. Diplomats in China also reported mysterious sounds and symptoms, still unexplained. But for now it seems that the noise at the heart of the Cuban incidents probably has a benign origin.

Somewhat ironically, one of the first diplomats to hear the noise was tantalizingly close to the right answer. As reported by ProPublica, he blamed cicadas (which are not crickets, but do also sing). “Cicadas don’t sound like that,” his neighbor reportedly said. “It’s too mechanical-sounding.” But the Indies short-tailed cricket is no ordinary singing insect. It has the fastest pulse-repetition rate of any cricket in the Caribbean or North America. Have a listen. It sounds pretty mechanical!

The cricket story reminds me of a very similar saga: the Sausalito hum. Back in the 1980s, just across the bay from San Francisco, the people of Sausalito were kept awake by a loud, rumbling hum, which reverberated through the walls of their expensive houseboats. Some thought it was effluent being pumped from a sewage pipe. Others blamed a cable recently laid by an electric company. Yet others suspected Russian submarines.

But John McCosker from the California Academy of Sciences eventually showed that the hum was the love song of the male plainfin midshipman—a type of toadfish. These fish attract females by vibrating their swim bladder, the same organ that keeps them afloat, to produce an extremely loud noise that sounds more like a foghorn than a fish. When many males sing en masse, the ruckus can be heard on land, in Sausalito, Seattle, Southampton, and everywhere else that toadfish are found.

https://www.youtube.com/watch?v=vSmEsuhEDK0

These noises sound strange, unnatural, and even mechanical because most of us have absolutely no idea what the vast majority of animals sound like. Here, for example, are some lynx that (starting about 40 seconds in) wail like drunk banshees.

Imagine hearing that in the dead of night. Or a brushtail possum, sounding like grinding machinery.