Do inaudible sonic weapons exist?

Question

The US is investigating whether diplomats in Cuba were subjected to a sonic weapon that caused hearing problems:

• The Guardian, 11 Aug 2017

One or more Canadians affected after suspected use of sound weapon against US personnel in Havana led to expulsion of Cuban diplomats from Washington

[...]

In the autumn of 2016 a series of US diplomats began suffering unexplained losses of hearing, according to officials with knowledge of the investigation into the case. Several of the diplomats were recent arrivals at the embassy, which reopened in 2015 as part of President Barack Obama’s re-establishment of diplomatic relations with Cuba.

Some of the US diplomats’ symptoms were so severe they were forced to cancel their tours early and return to the United States, officials said. After months of investigation US officials concluded that the diplomats had been attacked with an advanced sonic weapon that operated outside the range of audible sound and had been deployed either inside or outside their residences.

On the scientific side, is it plausible the existence of these "sonic bombs" that go undetected by the victim? This article in a (more or less) scientific site suggests two mechanisms:

The IFLScience! website conjectured about the technology:

The curious thing about these incidents in Havana, though, is that the suspected sonic devices haven’t been accompanied by audible noises. They appear to be operating at a frequency beyond that of human hearing, and yet they’ve reportedly caused hearing loss and headaches in the targets.

There are two ways in which this could be achieved. The first would be to use microwaves. Imperceptible to people lacking detection technology, it has been shown that small beams directed at people’s heads rapidly heat tissue within the brain, generating a small shockwave. [...]

Infrasound – sound that is at a lower frequency than the range that’s picked up by human hearing – can also cause hearing loss in some cases. According to the US National Institutes of Health, being exposed to concentrated infrasound can cause “fatigue, apathy, and depression, pressure in the ears, loss of concentration, drowsiness, and vibration of internal organs.”

At this stage, it’s deeply unclear which is more plausible – but the point is that “silent” acoustic weapons do exist, and they certainly could have been deployed in Havana.

The IFLscience article references a document by the US NIH. But this document itself, on page 9, states that

One argument against the feasibility of the use of infrasound in nonlethal weapons is that infrasound's wavelengths (17 m and above) are so long that they spread out too rapidly to be focused".

Is the existence of such "sonic bombs" plausible?

Answer 1

The 2020 IOM report on "Havana syndrome" only considers RF (radiofrequency) as the kind of directional phenomena/weapon that could have caused the reported symptoms.

They've not mentioned anything sonic (i.e. transmitted as air pressure changes) instead of electromagnetic as being worth considering as alternative explanation, although they do go over a number of alternatives including chemical, infectious, and psychosocial.

There is no explicit reasoning given why they didn't bother considering sonic weapons at all.

On the other hand, one of the experts consulted, in an interview with WebMD, didn't totally exclude some kind of ultrasonic device:

James Giordano, PhD, a professor of neurology at Georgetown University and senior fellow in biosecurity, technology, and ethics at the U.S. Naval War College, has consulted for the government on the syndrome and has access to data and medical records from the attending doctors in Havana. He was asked to help explain the illness and what might have caused it. [...]

Giordano dismissed the possibility that the effects were due to either accidental or deliberate exposure to a toxic chemical, pesticide, or drug. No traces of any such agent were ever found in the homes or bodies of those affected. Instead, he thinks the most likely cause was some kind of mechanical device emitting ultrasonic or microwave energy. "This is the primary possibility with high probability," he says.

The known anti-personnel microwave weapons developed for the US military exhibit a burning sensation on the target/victim, so questions remain as to how the alleged RF attacks were carried out without this effect predominating. The main working theory for how RF caused the sound symptoms seems to be the Frey effect (it's mention a dozen times as least in the IOM report), but this has been studied less and hasn't been weaponized to date, at least according to what's publicly known. How the longer term symptoms were caused seems even less understood, e.g. Giordano said that

exposure could potentially create bubbling in the fluid inside a person's ear, and those tiny bubbles could cascade through the blood to the brain, causing damage similar to the decompression sickness some scuba divers experience.

I have no idea how plausible this particular mechanism is, in the opinion of other experts.

At least a couple of US microwave weapon experts have discounted that loud sound could be reasonably be experienced via RF without burning or even deadly injuries occurring first:

There is no way the ray gun could deliver sound loud enough to be annoying at nonfatal power levels, says Kenneth Foster, a bioengineering professor at the University of Pennsylvania who first published research on the microwave auditory effect in 1974.

”Any kind of exposure you could give to someone that wouldn’t burn them to a crisp would produce a sound too weak to have any effect,” Foster says.

Bill Guy, a former professor at the University of Washington who has also published on the microwave auditory effect, agrees. ”There couldn’t possibly be a hazard from the sound, because the heat would get you first,” Guy says.

Guy says that experiments have demonstrated that radiation at 40 microjoules per pulse per square centimeter produces sound at zero decibels, which is just barely in hearing range. To produce sound at 60 decibels, or the sound of normal conversation, requires 40 watts per square centimeter of radiation. ”That would kill you pretty fast,” Guy says. Producing an unpleasant sound, at about 120 decibels, would take 40 million W/cm2 of energy. One milliwatt per square centimeter is considered to be the safety threshold.

N.B. the 2018 JAMA report on the initial (21 cases) included sound that was "directional, intensely loud, and with pure and sustained tonality [...] high-pitched sound was reported by 16 (76%) although 2 (10%) noted a low-pitched sound [...] Owing to security concerns, further details of potential dosage cannot be provided." So it seems some gap remains on explaining how microwaves could have caused that "intensely loud" sound but not burns.

There is an (older) 2017 NYT article that has experts chiming in on the ultrasound hypothesis. The main issue with that seems to be that it's not clear how feasible the attack(s) would have been given how fast ultrasound pressure decays in air:

“Ultrasound cannot travel a long distance,” said Jun Qin, an acoustic engineer at Southern Illinois University. The further the sound goes, the weaker it gets. And, noted Dr. Garrett, humidity in a place like Havana would weaken it still more. [...]

An ultrasound-emitting device planted inside a building, on the other hand, might be close and powerful enough to cause harm to occupants. But even an interior wall would block its waves.

A smaller emitter placed even more closely, perhaps in someone’s pillow, might do the trick, said Dr. Qin. But it’s hard to believe such a device could escape attention. In theory, a building could be packed with small emitters; however, experts called it unlikely.

For what's worth it, AP released in 2018 a recording of what some of those involved in the incidents supposedly heard. But the US officials refused to confirm its authenticity and its relevance to the alleged attacks.

A recently declassified (via FOIA and with numerous blanked-out passages) 2018 report by a rather obscure JASON group said in its main findings that:

No plausible single source of energy (neither radio/microwaves nor sonic) can produce both the recorded audio/video signals, and the reported medical effects. [...] The recorded audio signal is, with high confidence, not produced by the nonlinear detection of high power radio frequency or ultrasound pulses. [...] We judge as highly unlikely the notion that pulsed RF mimics acoustic signals in both the brain (via the Frey effect) and in electronics (though RF interference/pickup). [...] It cannot be ruled out that the perceived sounds, while not harmful, are introduced by an adversary as deception so as to mask an entirely unrelated mode of causing illness in diplomatic personnel.

Much later in the JASON report, in an area where 99% of the text is otherwise blanked, it's mentioned that a possible source of the sound as heard might be a high-cycle concrete vibrator. If you don't know what that is or what it sounds like, see this vid.

Regarding ultrasound, while noting that it could be source of audible effects e.g. via intermodulation distortion, as source of physiological damage, the JASON report notes that

However, such lesions require direct contact with ultrasonic transducers.

Answer 2

Possibly. There have been many advances in acoustics, especially in the application of ultrasound, that may explain that incident in Cuba.

The Incident

In 2017, US diplomatic staff began to suffer mysterious traumatic injuries that have now been dubbed “Havana syndrome” by the US and Canadian media. The diplomats stationed in Cuba initially referred to the phenomenon as “The Thing“ whereas University of Pennsylvania specialists who examined victims brought back from Cuba gave it the name "Immaculate Concussion".

So far, it has affected US and Canadian diplomatic staff in Cuba and US diplomatic staff in China. The symptoms are more serious than just hearing loss and have since been confirmed to constitute a form of brain damage. The physical symptoms are:

• (from initial reports) “hearing, cognitive, visual, balance, sleep and other problems”.

• (from Senate congressional hearings) “sharp ear pain, headaches, ringing in one ear, vertigo, disorientation, attention issues and signs consistent with mild traumatic brain injury or concussion”.

• (from an State Department email alert to US embassy staff in China) “dizziness, headaches, tinnitus, fatigue, cognitive issues, visual problems, ear complaints and hearing loss, as well as difficulty sleeping”.

The official response (Cuban incidents) ---------------------------------------

• White House chief of staff John Kelly:

“We believe that the Cuban government could stop the attacks on our diplomats”.

• President Donald Trump:

“I do believe Cuba’s responsible. I do believe that […] it’s a very unusual attack, as you know. But I do believe Cuba is responsible.”

• Secretary of State Rex Tillerson described the injuries as “health attacks” during a joint with the Canadian Foreign Minister.
• The state department recognised 22 Americans that are “medically confirmed” to be affected. This figure grew to 24 by 2018.
• Canada halved its number of diplomatic personnel in Cuba.
• Global Affairs Canada ended family postings to Cuba and withdrew all staff with families.
• The US expelled 15 Cuban diplomats in retaliation.
• Cuba denied involvement in the attacks.

The official response (Chinese incidents) ----------------------------------------- - statement: > “[The State Department received medical confirmation that a U.S. government employee in China suffered a medical incident consistent with what other U.S. government personnel experienced in Havana, Cuba][8].” - State Department warning sent to staff via email: > anyone who experiences "[unusual acute auditory or sensory phenomena][9]" while in China should move away from the source of the noise. - [affected staff at the American Consulate in Guangzhou are evacuated][10]. The remaining staff and their families underwent testing by medics from the the State Department.

• China’s Foreign Minister:

“We don’t want to see that this individual case will be magnified, complicated or even politicized. We hope people will not associate it with other unnecessary matters.”

• U.S. Secretary of State Mike Pompeo:

“We notified China of what took place as best we know it and they have responded in a way that is exactly the right response.”

The Sound ([from Cuban incidents via AP][2]) --------- https://youtu.be/Nw5MLAu-kKs

The Associated Press has obtained a recording of what some U.S. Embassy workers heard in Havana in a series of unnerving incidents later deemed to be deliberate attacks. The recording, released Thursday by the AP, is the first disseminated publicly of the many taken in Cuba of mysterious sounds that led investigators initially to suspect a sonic weapon.

The recordings themselves are not believed to be dangerous to those who listen. Sound experts and physicians say they know of no sound that can cause physical damage when played for short durations at normal levels through standard equipment like a cellphone or computer.

The sound seemed to manifest in pulses of varying lengths — seven seconds, 12 seconds, two seconds — with some sustained periods of several minutes or more. Then there would be silence for a second, or 13 seconds, or four seconds, before the sound abruptly started again.

A closer examination of one recording reveals it’s not just a single sound. Roughly 20 or more different frequencies, or pitches, are embedded in it, the AP discovered using a spectrum analyzer, which measures a signal’s frequency and amplitude.

To the ear, the multiple frequencies can sound a bit like dissonant keys on a piano being struck all at once. Plotted on a graph, the Havana sound forms a series of “peaks” that jump up from a baseline, like spikes or fingers on a hand.

“There are about 20 peaks, and they seem to be equally spaced. All these peaks correspond to a different frequency,” said Kausik Sarkar, an acoustics expert and engineering professor at The George Washington University who reviewed the recording with the AP.

The multiple peaks could be accounted for if the alleged sonic device is a phased array speaker made of multiple ultrasound transducers. Phased array speakers are used to "steer" and "aim" sounds without actually changing the position of the speakers. Phased arrays work by exploiting acoustic interference timed in order to propel a wave in a particular direction.

Besides the discordant phase effect little else is known about the sound itself.

Clinical features of “Havana syndrome” ([July 2019][12]): --------------------------------------------------------- > - Mean whole brain white matter volume was significantly smaller in patients compared with controls, with no significant difference in the whole brain gray matter volume.

• There were significantly greater ventral diencephalon and cerebellar gray matter volumes and significantly smaller frontal, occipital, and parietal lobe white matter volumes; significantly lower mean diffusivity in the inferior vermis of the cerebellum; and significantly lower mean functional connectivity in the auditory subnetwork and visuospatial subnetwork but not in the executive control subnetwork.

This profile is close to leukariosis, a kind of white matter disease caused by, ordinarily hypertensive, injury to small blood vessels that supply cortical white matter around the parietal lobes. Leukariosis is a precursor to the dementia known as “Binswanger’s disease” but the progression doesn't always happen.

We now know that the injury is real. The US and Canadian reaction has been to accuse Cuba of foul play, to expel Cuban diplomats and to repatriate non-essential staff as well as family members to the home country. This reaction is consistent with a real perceived threat. There is obviously something hurting these diplomats but there's no evidence that the cause was a "sonic bomb".

Sound can be used to cause harm to humans in a variety of ways.

Loud Noises

Injury to the inner ear. Loud sounds can rupture parts of the inner ear. This is a well known cause of hearing loss. According to the National Institute on Deafness and Other Communication Disorders, sounds [above 85 dBA are potentially injurious][13] but this figure is sensitive to the frequency of the sound. High decibel sounds dissipate too quickly to make for effective weapons. Their range is too short.

High-intensity focused ultrasound (HIFU) ablation

Ultrasound focused by a lens to a high pressure is capable of causing injury inside the body at the focal point. This technique is called [high intensity ultrasound therapy][14] and is used to treat small tumors non-invasively. In therapy, the mechanism used is usually hyperthermic (and therefore cannot be the cause of Havana syndrome) but can also be mechanical. Mechanically, [lesions can be opened inside an organ via acoustic cavitation of bodily fluids][15]. The high energy sound waves disturb bodily fluids causing bubbling. The increased pressure inside a sac or vessel will open a lesion.

High intensity ultrasound necessary for concussion could be achieved by using an array system of ultrasound transducers. This is consistent with descriptions of the injury as immaculate (focused) concussion by specialists.

Concussive force starts above 85 g-force with the average concussion being at 95 g-force.

Sonosensitisers and Sonodynamic therapy

In medicine, sonosensitisers are chemicals that, in solution, oxidize when treated with frequencies of sound. The chemical phenomenon is known as [acoustic cavitation][17] and its use biomedically is known as [sonodynamic therapy][18]. Sonosensitisers are often chemicals that release reactive ions that cause chain reactions that release chemicals toxic to cells. Many are also photosensitisers. An example is [Copper Cysteamine][19] which releases the [Cu+ supercation that reacts with water to produce reactive oxygen species][20] that cause necrotic cell death.

Doctors can deliver these cytotoxins to targeted tissues by conjugating the individual nanoparticles with antibodies. This is known as immunochemical passive targeting. Adapting these cytotoxic drugs for oral delivery is feasible, less harmful copolymerizing medicines have been, but is not practiced in cancer therapy because of the dangers. In addition, other sound-sensitive nanoparticles exist that rely on piezoelectric principles to cause cell death. This is the same technology used in leadless, batteryless pacemakers. Finally, there are also antibodies that bind to small vessel endothelial cells in the central nervous system. These are supposed to be used for drug delivery behind the blood–brain barrier.

A nation-state actor, if so inclined, could repurpose medical innovations in order to manufacture a sound-responsive poison that causes "mild traumatic brain injury" deleterious to white matter. This explanation is consistent with the claims of former NSA officer, Mike Beck, who claims have developed Parkinson's disease, along with a colleague while stationed in China. Beck thought a microwave weapon might be responsible. This explanation is undermined, however, because specialists who inspected the first returnees from Cuba reportedly found no evidence of a toxin.

Answer 3

In 2008, WIRED magazine came out with this article: "Sonic Blaster + Laser = New Weapon"

Imagine being hit by a nonlethal blast that seems to explode in front of you – a deafening and blinding combination of light and sound. As the battle for "sonic blasters" heats up, a number of companies are looking at innovative ways to combine light and sound into new, nonlethal devices. One company, Wattre Corp., is working to couple its acoustic technology with a nonlethal laser. In a recent interview with DANGER ROOM, Curt Graber, president of Wattre Corp. explained this newfangled device, which puts together the company's collimated beam of sound with another firm's laser (which creates a sort of mid-air plasma ball). "It’s a laser that basically ignites the air in front of the person," Graber says. "It creates fireworks right in front of you."Hs60_promo_big

The combined effect is what Graber calls a "psycho-acoustical event."

Wattre's technology, called Hyperspike, is a Guinness Book of World Records winner for "loudest speaker." As for the laser portion, produced by a company called Stellar Photonics, DANGER ROOM's David Hambling actually has a good writeup of the technology at New Scientist. "The device uses a technology known as dynamic pulse detonation (DPD). A short but intense laser pulse creates a ball of plasma, and a second laser pulse generates a supersonic shockwave within the plasma to generate a bright flash and a loud bang," he writes. The Plasma Acoustic Shield System will eventually combine a dynamic pulse detonation laser with a high power speaker for hailing or warning, and a dazzler light source."

While the combined sound/laser weapon is certainly a novelty, Wattre Corp. has its eye on the growing long-range hailer market. It competed for a recent Navy contract that was ultimately awarded to American Technology Corp., which produces the Long Range Acoustic Device (Wattre protested the contract award; Graber says the Hyperspike technology has better beam forming capabilities in the human voice range, among other advantages).

While Wattre lost its protest, they've sold units to foreign navies, among other customers; Wattre has also made sales to France for riot control. "Now it’s just a mater of people trying to figure out the best possible usage," he says.

According to Wikipedia, the range of frequencies that people hear is from 20 - 20,000 cycles / second. But according to Electronics.StackExchange contributor Chris Stratton:

Can computer speaker emit ultrasound?

Generally, yes (confirmed by both theory and experiment) though probably not as effectively as they can lower frequencies.

Provided that ordinary computer speakers may emit inaudible sound...

YES!

It is most certainly plausible that the engineering work of Wattre Corp or other researchers could produce directed sound waves that are both inaudible and high-energy, in parallel with the ongoing work developing sonic weapons that are deafening and blinding.