Even low-dose ultrasound (what they use on pregnant woman) results in ultrastructural changes in brains [0], specifically at the nodes of Ranvier (the gaps between myelin along axons). See also [1] for a review.
[0] Ellisman MH, Palmer DE, André MP (1987), "Diagnostic levels of ultrasound may disrupt myelination," Experimental Neurology 98:78–92 https://pubmed.ncbi.nlm.nih.gov/3308504/
[1] Quarato, C.M.I., Lacedonia, D., Salvemini, M., Tuccari, G., Mastrodonato, G., Villani, R., Fiore, L.A., Scioscia, G., Mirijello, A., Saponara, A. and Sperandeo, M., 2023. A review on biological effects of ultrasounds: key messages for clinicians. Diagnostics, 13(5), p.855. https://pmc.ncbi.nlm.nih.gov/articles/PMC10001275/
All sound is vibration, so everything is affected by sound at some point as the vibrations propagate through and physically move around materials. Humans can hear because the audible frequency range moves receptors in human inner ears, and as you can imagine this isn't local to the ear, the whole brain will be affected (but biology has accounted for this). If you knock on wood that sound is audible in many frequencies--below human audible, audible and also above human audible (what we call 'ultrasound'). What is more dangerous generally is sustained noise at any frequency; lower frequency + high amplitude is one of the most harmful as that can physically push you.
>sustained noise at any frequency is dangerous
is this your conclusion? are there any studies you can link? thanks.
Interesting, if ultrasound effects the brain, then maybe specific pattern could be used to non-destructively stimulate it?
There's Ultrasound DBS Deep Brain Stimulation.
/? ultrasound brain stimulation: https://www.google.com/search?q=ultrasound+brain+stimulation
There's ultrasound for Alzheimer's, which may not be about Amyloid Tau;
"Improving Cognition Without Clearing Amyloid: Effects of Tau and Ultrasound Neuromodulation" (2024) https://journals.sagepub.com/doi/10.3233/JAD-240616 ... https://scholar.google.com/scholar?cites=1746486614029868186...
Also, Beta-Cyclodextrin apparently reverses atherosclerosis in the body and brain - by "absorbing" sugar-alcohol FWIU - and it's already approved but we don't know what dose is low enough to be safe.