picture: 123RF/Valerii Khadeiev
picture: 123RF/Valerii Khadeiev

In 2016 employees of the American consulate in Havana, Cuba, began hearing strange sounds and vibrations. A short while after the sounds first began, 24 workers at the consulate fell ill.

Headaches, dizziness, nausea, loss of hearing, brain swelling and minor memory loss were their symptoms, which match those of a mild traumatic brain injury.

The US government cried foul, blaming Cuba for the incident or at least for failing to protect the US citizens affected by the "attack" between December 2016 and August 2017. It led to the expulsion of 17 Cuban diplomats and increased the animosity between the two nations.

Then the sound stopped.

But the strange incident appears to have resurfaced in China in May. Initially just one person was evacuated from a US government facility after displaying "similar signs" of possible brain injury after hearing strange sounds. But that figure has since risen to 11, eight of whom are Americans associated with its consulate.

And the sound may be on the move. It appears to have spread across the People’s Republic from the initial attack site in Guangzhou to Shanghai and Beijing where three victims were reportedly evacuated for medical tests in the US. And another American displayed the same symptoms in Havana at the end of June.

Based on a six-second clip recorded by Associated Press in Havana, the sound is something akin to that of a high-pitched cicada. The first victim of the Guangzhou incident, Mark Lenzi, a security engineering officer at the consulate, describes the sounds as "marbles rolling around a metal funnel".

Listening to the AP recording, which is available on YouTube, does little more than annoy. So it is no wonder that experts across the scientific community and government are left flummoxed.

These incidents are not the first that the world would have heard from sonic weapons. Long-range acoustic devices have been on the market for well over a decade, seen in reports dating back to 2005 when the US Navy successfully used a sonic cannon to subdue a group of Somali pirates. Since then they have been used frequently as crowd control by the Israeli Defence Force and by the US police force — most frequently against peaceful protesters.

Then there is "The Mosquito", a device that omits a 17kHz whine audible only to teenagers. Our ears change shape as we age, making adults unable to hear the piercing buzzing tone used in the UK, over the past 10 years, to deter teens from loitering.

Directional sound technology has also evolved to the point that only those standing directly in front of the speaker can hear the noise. Everyone else is unaffected.

But are these James Bond-like weapons real? Could they have been fashioned in a secret government lab somewhere?

That may be the case, but some scientists are calling foul.

Even with AP’s recording, some speculate that the weapons’ true power may come from "inaudible" sound frequencies. Others question their existence entirely.

"I’d say it’s fairly implausible," Jürgen Altmann, a physicist at the Technische Universität Dortmund in Germany and an acoustics expert, told The New York Times.

Infrasound, a tone that transmits at a lower bass, which is capable of causing people to become nauseated, is difficult to direct.

So the case of only Americans being affected by sonic weapons and not the rest of the dense inner-city populations of Havana and the Chinese metropoles seems implausible.

On the other side of the spectrum, ultrasound, which is anything pitched higher than 20kHz, is very directional and can damage tissue — it killed a mouse at close range in an experiment in 2005. However, ultrasound disperses at long range and has a tendency to dissipate when it hits walls, even in close proximity.

So that theory may not hold up, because the US consulate in China is a relatively new, highly secure box-like building specifically designed to withstand electronic eavesdropping.

Even if the weapon were made up of tiny emitters that scatter around the interior of a building, there would be ample evidence of its existence and it wouldn’t be able to move around China with such ease. Instead, some experts say that toxins, environmental or even physiological factors could have caused people to fall ill.

While the illness remains unsolved, trade relations remain prickly between the US and China. And Cuba has yet to hear an apology for kicking out its diplomats. Though some US officials believe Russia may be a more obvious culprit for the attacks in former adversaries, Donald Trump’s warm relations with Russia’s Vladimir Putin may quash that line of inquiry.

Strange noises are still being heard and so far 36 people have been shuffled off to the Center for Brain Injury & Repair at the University of Pennsylvania. We shall have to wait to hear more.