I feel like we are ways out from seeing anything like it. From what I’ve seen non-Newtonian fluids typically take a decent amount of energy to stop something and sound wouldn’t have much energy compared to something like a bullet.
On a sidenote does Decibullz own a patent on percussive hearing protection or am I looking up the wrong term? I feel like there must be other hearing protection out there that is effective against sudden loud sounds.
Compression thickening/thinning, which only starts after a certain rate of change. I’m not sure what materials have such a property. Then, you’d incorporate it into a composite which dissipates sound selectively in one state. One idea is a fibers of a material that matches the impedance of the fluid during quiet periods, but scatters it as impedance shifts during high-energy periods.
Maybe you could use standard shear thickening somehow, but it would be a lot harder as sound only travels through air compressively.