The US is investigating whether diplomats in Cuba were subjected to a sonic weapon that caused hearing problems:
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! web-site 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?