Meta materials coming to audio?

Read an interesting article about meta materials being used in speaker design to absorb the back wave off the drivers. To my limited understanding, this could be pretty revolutionary. Has anyone heard a meta material dampened speaker yet?

https://darko.audio/2020/09/kef-tease-metamaterial-absorption-technology/

https://phys.org/news/2019-03-acoustic-metamaterial-cancels.html

https://www.frontiersin.org/articles/10.3389/fmats.2019.00182/full

 

Interesting stuff.
I would predict it is more of a marketing fluff for speaker damping as there are not that many issues with damping in speakers. Some speakers use no damping and sound good (with complex internal geometry with minimal standing waves).
It would be revolutionary for room acoustics. Wideband absorber no thicker than a fist.

 

Hadn’t thought about room acoustics but you’re right. Obviously there’s a lot of intellectual property in the design of the surface, but 3D printing makes fabrication simple.

 

Imagine being able to wall off part of a room in which one could listen to anything, any volume, without bothering anyone else. Floor and ceiling too.

Or shut out the world and listen to nothing in peace.

Wow.

 

Man, isn't there something about how there's no such thing as total silence... You're left with nothing but the deafening sounds of your stomach noises, heartbeat, your swallowing and the inherent ringing in your ears.

 

Yeah. Potentially great uses for things in the EM spectrum, but acoustics?... eh, that's a bit of a ways off yet. The rough premise is the same, but right now their applied acoustic models are more like tuned resonators for specific frequencies (1) which to my eye could be either for absorption or emitting an out of phase signal to partially cancel the original, or both, or clever path lengthening mechanisms.

(1) this would be great for machinery that produces a specific noise that you want to reduce, but practically useless for a speaker except in the case of there being a particular unwanted resonance in your cabinet or port(2)

(2) except then you would probably be better off designing to avoid that unwanted resonance (3)

(3) here's an example of the Pioneer RM-07 monitor which has a similar-ish resonator built off the port: https://www.soundonsound.com/reviews/pioneer-rm-07

 

I've spent a bit of time in anechoic chambers in my university days. If you really settle down, eventually you become conscious of the fact that your breathing is too loud and you start questioning your ability to breathe. You will start to hear your heartbeat, then eventually a whooshing sound which I think was the sound of bloodflow in my ears. Swallowing becomes absurdly loud and it throws off your sensitivity for a few seconds.

 

Lol... I was thinking bit-of-peace quiet, rather than anechoic silence!

(which I'd like to experience).

I'm sure you're right... I'll file my dreams under still-science-fiction. But it's a step in the right direction.

 

I'd need to go back and do some googling, but wasn't one of the bigger speaker manufacturers playing with using sea-foam based ceramics as internal absorbers? Take a piece of sea foam, dip it in porcelain slip and fire it, viola, complex multi-band absorber?

 

Haha, would be interested to know if your internal dialogue outweighed your other body sounds in there. I remember reading about people going totally mental when confronted with absolute silence. It would be a party for sure.

 

Only time I’ve been in an anechoic chamber was when getting my hearing tested. I wasn’t in there all that long. I found the experience oddly calming and slightly uncomfortable. The lack of external background noise allowed me to focus attention on sounds easily, but it’s like the squelch was turned all the way down and volume turned all the way up.

 

Years ago I camped out in the middle of the Negev desert (Israel) for a single night. No lights, no other sign of civilization. The silence was, truly deafening it was actually uncomfortable to have no ambient background noise.

 

Alternative is to look for old room used by spies!

I worked on one building reconstruction (previously ministry of foreign affairs) and inside was one extremely insulated room, assumption was that it was used for communication with Moscow during cold war.