Sound blocking shape

usp1 · « **on:** 13 Mar 2019, 09:20 pm »

I found this idea very intriguing. Imagine having this as a noise canceling headphone!

https://www.fastcompany.com/90316833/scientists-have-discovered-a-shape-that-blocks-all-sound-even-your-co-workers

richidoo · « **Reply #1 on:** 14 Mar 2019, 12:33 am »

That's very interesting. Thanks for posting the link!

JLM · « **Reply #2 on:** 14 Mar 2019, 09:57 am »

Curious to learn more about this. Is it the shape or the material that causes the effect? By what means? How could it be applied to any situation as implied? Is it directional? What frequency range is it effective in and can a given frequency be targeted?

Is it via disruptive interference? Note that vibration isolators are already available for HVAC applications where high air flow yet quiet is required (like operating rooms) where the fan has to be close by. On cars they're called mufflers.

usp1 · « **Reply #3 on:** 14 Mar 2019, 02:16 pm »

All good questions JLM! I am trying to find out more details. Since it is 3d printed, the material itself cannot be too exotic. More likely it is a shape (as the article title implies) but it is possible that there are complex channels and voids in the annular ring. I am also not sure if the attenuation occurs at any point after the device or if there is a lensing effect that creates a null at the microphone. Other questions to consider - Are the devices stackable to attenuate even more? Is it a broad spectrum attenuator or designed for specific frequencies? Is the initial pipe needed to channel the sound into the device? Is the length of the pipe critical to the attenuation?

I need to find the actual research paper instead of the popular press article to know what the device does. As shown in the video, it seems like something that is suitable as an automobile muffler.

P.S.
Here is a better link https://www.eurekalert.org/pub_releases/2019-03/bu-brd030619.php with more detail.

And the journal article - https://journals.aps.org/prb/pdf/10.1103/PhysRevB.99.024302

usp1 · « **Reply #4 on:** 14 Mar 2019, 02:54 pm »

I am not a physicist and don't understand all the details but it seems that the device is tuned to specific frequencies and is not a broad spectrum device. It has six helical waveguides in the annular ring and apparently the device is tunable based on the helical channel cross-section, helix angle and the inner diameter of the device.

Mike B. · « **Reply #5 on:** 14 Mar 2019, 08:30 pm »

I can hear it works in a confined space. How does it translate to a room. I am thinking this might only have specific applications. Headphones, ear protection, etc.