On August 10, HHTM reported several Americans at the US Embassy in Havana, Cuba began suffering from unexplained medical symptoms late last year. That report cited a Washington Post article, which described the situation as an “acoustic attack” on Americans at the Embassy in Havana. According to several subsequent follow up reports in the press, victims described several ear-related symptoms, including dizziness, balance problems and hearing loss. In addition, nausea, memory lapse and headaches have also been common symptoms.
Reports of noise heard by the victims at the site of the apparent attack have varied. Some of those injured in the attack say they heard nothing, while others have reported hearing deafening sounds. Many reputable news outlets initially reported either infrasound (sound below 20 Hz) or ultrasound (sound above 20,000 Hz) to be the most likely explanation, but recent speculation centers primarily on infrasound as the culprit.
Infrasound Weapon Behind Acoustic Attack in Cuba?
Infrasound, though normally considered inaudible, is audible to some sensitive people, especially if the intensity level is sufficiently high.
As the investigation continues to unfold and we learn more, HHTM reached out to Jerry Punch, audiologist and emeritus professor at Michigan State University for comment. Dr. Punch is recognized as a leading expert on industrial noise, and some may recall in 2014 he contributed a three-part series to the HHTM blog on the adverse health effects of wind turbine noise.
Punch told HHTM that “compared to ultrasound, infrasound travels farther because of its long wavelengths, is difficult to attenuate by traditional noise-control methods, and potentially affects more people because it is broadly distributed. Paradoxically, infrasound would seem a poor choice as a weapon to be used deliberately against diplomats because it can’t easily be targeted toward specific individuals. Others who’ve not yet experienced symptoms may be affected, whether or not the attacks are deliberate, if the situation continues. If and when the attacks stop, it is likely that symptoms such as headache, dizziness, and nausea will subside. That would be consistent with news reports that symptoms stop when diplomats leave their areas of residence, and with the experiences of people who suffer adverse health effects, among them sleep disturbance, while living near wind turbines. Those individuals typically report that symptoms disappear when they leave their residences and reappear when they return home. Some have abandoned their homes altogether to escape the negative health impacts.”
Source Behind Attack Still Unclear
Although the culprit of these acoustic attacks remain unknown at this time, Punch said, “theories abound as to whether infrasound is being used deliberately as a weapon for the purpose of harassment or whether it is being emitted accidentally—perhaps as a by-product of surveillance activities. The Canadian government has speculated that covert sonic attacks are being waged by a country, or countries, other than Cuba; accidental effects of surveillance by other countries cannot be ruled out.”
To date, the U.S. has expelled two Cuban diplomats in retaliation, and many American diplomats have cut their Cuban assignments short because of the incidents.
Historically, infrasound has been used as a weapon by militaries as a form of torture, by police departments as a means of crowd control, and by private companies for a variety of nefarious purposes. What makes infrasound the most likely explanation for these incidents is that it is known to produce the same types of symptoms being reported by these diplomats. Noise-induced Sick Building Syndrome in the 1970s and 1980s, caused by poorly designed heating, ventilating and air conditioning (HVAC) systems that produced infrasound, resulted in workers who experienced headache, mental fatigue, productivity loss, mood shifts, lowered social orientation, and cognitive dysfunction, which led to their not wanting to work in their offices. These symptoms also closely match those reported by a substantial number of individuals who live near industrial wind turbines, which are known to produce infrasound well below 20 Hz. It should be emphasized, though, that hearing loss thus far has not been seriously considered as a symptom of exposure to wind turbine noise.”
–Jerry Punch, PhD
Research Shedding Light on Impact of Infrasound
Punch, who has been involved in numerous studies and consulting projects involving industrial noise abatement, also shared that “researchers have recently shed light on the probable contribution of both the cochlear and vestibular components of the inner ear to many of the negative symptoms caused by infrasound. For example, Alec Salt and colleagues at the Washington University School of Medicine in St. Louis, Missouri, have shown that infrasound can be transmitted to the brain via the outer hair cells, but not the inner hair cells, of the cochlea. The infrasonic energy apparently stimulates portions of the brain associated with the auditory cortex, where it is perceived as unpleasant sensations, as opposed to hearing. There is also well-structured speculation, based on limited scientific evidence, that infrasound accelerates the flow of endolymph within the vestibular system, resulting in a sensation similar to motion sickness, or seasickness. The seemingly credible notion that motion sickness may involve an intermodal sensory conflict between visceral graviceptor signals and vestibular stimulation has also been advanced. The concept that infrasound might cause vestibular disturbance also seems to explain the onset of such symptoms as dizziness, unsteadiness, nausea, vertigo, headache, mental disorientation, and sleep disturbance.”
As experts continue to unravel the mysteries surrounding the weaponization of sound, this story should remain of tremendous interest to audiologists and others in the hearing industry.
As Dr. Punch emphasized, learning more about the roles played by the inner ear and the brain in mediating negative health symptoms from inaudible sound can aid in clinical work with patients and demonstrate to the public that audiologists can contribute to the identification and treatment of conditions that stem from it.
*featured image courtesy Reuters