Hi !
I am both acoustician, enginner and accordion maker and I look for a meta material which could make a one way sound barrier.
Do you have any idea ?
I am both acoustician, enginner and accordion maker and I look for a meta material which could make a one way sound barrier.
Do you have any idea ?
Nearly all of them can do that. The main challenges are:
1) the metamaterial has to be quite large to work at a low frequency
2) 3D printing the metamaterials is tricky; if you wanted to print an entire wall of them, it would take weeks to finish the print.
All of the metamaterials are mostly just closed transmission lines, and you can simulate closed transmission lines in Hornresp.
To elaborate on that a bit:
A transmission line is tuned to a single frequency. You can make a transmission line that will attenuate sound to a high degree; 20dB of rejection is possible. A metamaterial is basically an array of those transmission lines. So you're creating a series of transmission lines, tuned to specific frequencies, to absorb sound.
Having said all that, I kinda lost interest in metamaterials for treating a room, because a couple of plants and a curtain are way less work, cheaper, don't look weird, etc. Sometimes the existing solutions are best.
IMHO, the best application of metamaterial is on the speaker driver itself, like KEF does
1) the metamaterial has to be quite large to work at a low frequency
2) 3D printing the metamaterials is tricky; if you wanted to print an entire wall of them, it would take weeks to finish the print.
All of the metamaterials are mostly just closed transmission lines, and you can simulate closed transmission lines in Hornresp.
To elaborate on that a bit:
A transmission line is tuned to a single frequency. You can make a transmission line that will attenuate sound to a high degree; 20dB of rejection is possible. A metamaterial is basically an array of those transmission lines. So you're creating a series of transmission lines, tuned to specific frequencies, to absorb sound.
Having said all that, I kinda lost interest in metamaterials for treating a room, because a couple of plants and a curtain are way less work, cheaper, don't look weird, etc. Sometimes the existing solutions are best.
IMHO, the best application of metamaterial is on the speaker driver itself, like KEF does
Ok, I would like to implement this in accordions, make a wall (approximately a4 format (210 x 287 mm size) so that the sound could go out but that extrenal sound could not pollute a internal microphone inside the instrument.
I wounder if it's possible to at least do a little improvement withing this size.
There is an exemple here : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910075/pdf/srep28023.pdf
but I don't really understand the design , ie how they mix the labythinth and the hybrid metastructure.
Few questions :
1) What is the minial surface of every transmission line ?
2) Does anyone made a parametric file on Cad software to design metamaterials ?
I wounder if it's possible to at least do a little improvement withing this size.
There is an exemple here : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4910075/pdf/srep28023.pdf
but I don't really understand the design , ie how they mix the labythinth and the hybrid metastructure.
Few questions :
1) What is the minial surface of every transmission line ?
2) Does anyone made a parametric file on Cad software to design metamaterials ?
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fyi i found these, there is the file ready to print designed my someone, its thick 1.2cm and can absorb 1 sabin at 125hz circa, someone has some news on this topic?
Thanks for posting that. Looks like the dimensions & makeup of the device is provided, but there's no 3D printable file, per se. The language is dense & technical enough that I'll have to read it again slowly, but definitely looks worth studying.
there is the file ready on the bambu studio app, i can right on print it! the file should be on maker world the website, and has to be found, i remember using the keyword like acoustic, or acousticpanel
https://secure.aes.org/forum/pubs/conventions/?elib=20758 .
They are designed to cover 150 to 20000 using 36 tubes times 4 in total 144 tubes . The heght of the absorber is 230mm. I’m using a 20 mm melamine foam between the absorber and driver.The absorber is 3D printed in pla. A bit of an effort to draw the design in fusion…
I have tried 3 versions of ”boxes” to my Walsh speakers closed box, tapered horn according to Terman/b&w nautilus patents and now also metamaterial-
The closed box creates a heavily box colouration of the sound.
The tapered horn is almost clean with some minor colouration.
The metamaterial is really clean with no noticable colouration.
Thomas
https://makerworld.com/models/134400
Edit I found the printable Stl, what I would like to know is that in what frequency region the absorption would change by scaling it up , now is tuned at 125hz , pretty damn impressive for 1.2cm
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No, it’s a Walsh driver.
https://patents.google.com/patent/US3424873A/en
Which is a bending wave speaker.
It has been a long struggle to find a solution to the ”box” that doesn’t colour the sound.
The meta material is extremly promising!
There’s a great post about metamaterials here:
Post in thread 'Acoustic Horn Design – The Easy Way (Ath4)'
https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-7904072
Post in thread 'Acoustic Horn Design – The Easy Way (Ath4)'
https://www.diyaudio.com/community/...-design-the-easy-way-ath4.338806/post-7904072
The thing that is impressive that is just soo easy to do , just a printed part with the hilbert infill and everything improved it’s truly impressive and makes me want to try it when I will start my project
@Sandasnickaren ....Curious, about the diameters top & bottom and centerline height of the very nicely done c/f cone.... 👍😎
Yeah, still around and playing about....
Yeah, still around and playing about....
Hej,
Yes I will share some new measurements. I'm preparing to do measurements of three versions of the "box".
1) closed box with damping material
2) reversed exponential horn similar to B&W nautilus
3) metamaterial
This will give me the opprtunity to compare the three solutions.
Thomas