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Comment by clairity | Hacker News Reader

ultrasounds are done on people all the time, especially during pregnancy on relatively fragile fetuses. we'd likely know of any serious risks by now. ultrasound is more akin to microscopic shaking than a mysterious flux of (highly potent) energy.

also consider that the cov2 virus is particularly fragile, for instance, requiring the external support of water to remain intact. it's why you don't need masks in most common situations (just distance), because the virus disintegrates so easily.

some viruses, on the other hand, can essentially hibernate and revive themselves once inside a host. those are the ones that would require enough excess energy that damage to other cells and organelles might be a genuine concern.

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The proposed ultrasound frequencies are 10-100 times as high as the ones usually used for imaging purposes, so the conclusion that it must be harmless does not naturally follow.

> "...vibrations between 25 and 100 megahertz"

"Ultrasound frequencies in diagnostic radiology range from 2 MHz to approximately 15 MHz" https://radiopaedia.org/articles/ultrasound-frequencies?lang...

So 10-50 times as high, but yeah.

But it's worth contrasting with focused ultrasound[1] which is used to either heat or shatter tissues, at higher frequencies and amplitudes.

1: https://en.wikipedia.org/wiki/High-intensity_focused_ultraso...

For a visualization, A lower frequency but high intensity method can be used to cook meat.

https://youtu.be/LHFhnnTWMgI

Agreed. You could substitute ultrasound waves with electromagnetic waves in this same conversation. We use EM waves every day for diagnotics -- at the 740-380nm range because that's visible light. 10x-100x frequency of that is ultraviolet, which is harmful. And as for resonant frequencies, it doesn't seem unreasonable to me that certain frequencies could denature certain proteins or have other effects.

i haven't delved into the specifics here, but note that a higher frequency doesn't necessarily mean a higher flux of energy, so that conclusion doesn't necessarily follow either.

It does not need a "higher flux of energy" to do damage. Exciting a system at its resonance frequency can increase the amplitude of its vibrations to the point that it gets damaged.

This does not take lots of energy, it does not take large amplitudes, just periodic input of power at the right frequency. Knowing that a system is fine at one frequency does not say (that) much about other frequencies.

yes, resonance can be significant, but that still doesn't necessarily mean that the energies here are significant, nor that the frequencies applied are the right frequencies, and resonant enough, for damage.

the underlying point is that unless we're capable of doing the relevant experiments ourselves, we need to trust that people in the field are cognizant enough to realize these obvious issues, test them, and report their findings. it's unlikely that lay people like us are going to find and gotcha the researchers in the field.

that's not to say that, in aggregate, we can't give researchers ideas about what to be researching. that, we can--and should--do, via conversations like this.

> yes, resonance can be significant, but that still doesn't necessarily mean that the energies here are significant, nor that the frequencies applied are the right frequencies, and resonant enough, for damage.

I did not claim that the proposed method has to be harmful. I stated that ultrasound imaging gives little to no insight in what happens at frequencies that are an order of magnitude or two higher than that. The second reply was an attempt to do away with the misconception that "higher flux of energy" was necessary for damage.

Great point. If you've never had an ultrasound, it's safe enough that the technician doing them (who may see dozens of patients in a day) isn't even wearing any shielding or protection.

Ultrasound is highly directed. The practitioner isn't getting exposed to a significant amount of ultrasound energy.

Not only is it highly directed, ultrasonic acoustical frequencies disperse very quickly in air. At 1MHz, the energy absorption in air is ~160dB/meter, so a person sitting at arm's length away from the emitter (even if it weren't highly directed) would receive ~6*10^-17 of the power (if that weren't far below any possible noise floor, which it is).

Good point, and a fair one. I would imagine though if there were any chance though they would have to be shielded.

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