On May 23, the U.S. embassy in China released a health alert, claiming that a U.S. government employee in China “recently reported subtle and vague, but abnormal, sensations of sound and pressure.”
Although the statement clarified that the United States did not know “what caused the reported symptoms” nor was aware of “any similar situations in China, either inside or outside of the diplomatic community,” the U.S. government sent a warning message to all its citizens in China in the health alert:
[I]f you experience any unusual acute auditory or sensory phenomena accompanied by unusual sounds or piercing noises, do not attempt to locate their source. Instead, move to a location where the sounds are not present.
An embassy spokeswoman also told CNN that this U.S. employee was diagnosed with a “mild traumatic brain injury.”
U.S. Secretary of State Mike Pompeo later claimed that this incident in China was “very similar” to and “entirely consistent” with those experienced by American diplomats posted in Havana, Cuba. Last year U.S. State Department sent most of its diplomats in Cuba home after accusing the Cuban government of conducting “sonic attacks” on employees of the American embassy.
Unsurprisingly, after Pompeo’s remarks the U.S. media then widely referred to this incident as a Chinese “sonic attack.”
However, many researchers believe that the symptoms these U.S. diplomats suffered are unlikely to be caused by “sonic attacks.”
Jürgen Altmann, a physics professor at Technischen Universität Dortmund in Berlin, told CNN, “I know of no acoustic effect that would produce concussion-like symptoms; according to my research, strong effects on humans require loudness levels that would be perceived as very loud noise while exposed.”
In line with Altmann, Wang Ning, chief physician of the Department of Neurosurgery in Beijing Xuanwu Hospital, who has specialized in the field of neurosurgery for many years, also told Chinese media that “To cause a ‘traumatic brain injury,’ the intensity of sound waves should be as strong as an explosive level.”
As for the earlier Cuba incident, many U.S. experts also ruled out the possibility of “sonic attacks.” For example, after examining the 21 embassy workers in Havana, a team of doctors at the University of Pennsylvania published a report on February 15 in the journal JAMA, suggesting that none of the proposed causes for these mass brain symptoms (including sonic weapons) really make sense, according to Live Science.
In fact, even the FBI made it clear that “there has been no evidence to support the theory of sonic waves being used to harm Americans in Havana.”
Instead, a group of scientists published an academic article, arguing that the Cuba incident was more likely the “accidental side effect of attempted eavesdropping.”
Kevin Fu, a researcher at the University of Michigan, together with Wenyuan Xu, a professor at Zhejiang University, in Hangzhou, China, and her Ph.D. student Chen Yan, published a report, titled “On Cuba, Diplomats, Ultrasound, and Intermodulation Distortion,” giving a more plausible explanation.
Through experiments, this team showed that ultrasonic signals from eavesdropping devices can “combine to produce audible and potentially dangerous tones similar to the undulating, high-pitched chirping that the diplomats described,” as Michigan News put it.
“We’ve demonstrated a scenario in which the harm might have been unintentional, a byproduct of a poorly engineered ultrasonic transmitter that was meant to be covert,” Fu told Michigan News. “A malfunctioning device that was supposed to inaudibly steal information or eavesdrop on conversation with ultrasonic transmission seems more plausible than a sonic weapon.”
IEEE Spectrum, a magazine edited by the Institute of Electrical and Electronics Engineers, believes that Fu’s report is “finally a likely explanation.” While Fu was quick to point out this is still just a theory, he suggested the harmful sound could be the unintentional result of an ultrasonic transmitter — an eavesdropping device — reacting with an ultrasonic jammer meant to safeguard against such bugs.
“Each device might have been placed there by a different party, completely unaware of the other,” Fu said.
Notably, this report was published in March, before the latest China incident.
So far, China’s attitude toward this incident has been quite calm.
On May 24, China’s Foreign Ministry responded:
China has always protected the safety of foreign diplomatic missions in China, including that of the U.S. diplomatic staff, in accordance with the Vienna Convention on Diplomatic Relations and the Vienna Convention on Consular Relations. Regarding what was said in those reports, China has carried out an investigation seriously and given an initial feedback to the U.S. By far, we have found no reason or clue for what was reported by the U.S.
In Fu’s mind, “bad engineering just seems much more likely than a sonic weapon.” If the China incident was “entirely consistent” with the Cuba “sonic attacks,” then it may be that a “poorly engineered ultrasonic transmitter” — or jammer, or both — was being used in both cases.