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Recent research into metamaterials for sound absorption -- any new products?

Wondering if anyone has heard of some new acoustic treatments for audio based on the following research (now 5 years old) into meta-materials:

https://www.sciencedaily.com/releases/2016/09/160920112321.htm

I found one brief further scientific paper, here: https://www.mwmresearchgroup.org/blog/archives/03-2020

And the application of such technology, here: https://www.sciencedirect.com/science/article/abs/pii/S0375960119303895?dgcid=rss_sd_all

"we propose an acoustic metamaterial for low-frequency (<500 Hz) absorptions, composed of three nested square split tubes with inverted opening directions. The efficiency of the absorber is investigated both numerically and experimentally, and absorptions at the peeks are found to exceed 90% and the frequency can be effectively adjusted by tuning its geometric parameters. We further test its yield strength under compression and confirm its buckling behavior happens from the outmost layer. This tunable acoustic metamaterial with a fairly good mechanical strength may lead to broad applications in noise reduction."

If these meta-materials are well-implemented into acoustic panels, building materials, etc. it seems that some real changes in room acoustic treatment might be on the horizon.

P.S. Some write about collecting energy from acoustic energy:

https://journals.sagepub.com/doi/full/10.1177/1687814017748077

"Therefore, many studies on self-powered electronic components by harvesting energy from ambient have been carried out, showing the potential benefit of eliminating the battery replacement and disposal. Acoustic energy is a clean, ubiquitous, and sustainable energy source, and it is abundant in some circumstances, thus investigating the acoustic energy reclaiming mechanisms is of significance."
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Showing 1 response by millercarbon

millercarbon's avatar
millercarbon
12,531 posts
 
You know the research is solid when they measure absorption at the peeks.

Meanwhile, there already are better alternatives to old-school acoustic treatments. By far the biggest improvement is to prevent energy getting into room structures in the first place. To do that simply put speakers and other components on springs. Ordinary springs like Nobsound help, but properly damped springs like Townshend are much better, probably because they directly target and damp resonance.

It is easy to read papers and posts and stuff, and conclude it is all about acoustic energy. For sure acoustic energy is involved. But it takes all of 30 minutes to prove mechanical energy can be many times greater a problem.

Then when it comes to acoustic treatment, Synergistic HFT are a lot more effective than old-school panels. Another one it takes only a little time to demonstrated.    

PS- The "peek absorption" thing they are talking about is called a Helmholtz resonator.
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