[abainbridge]

> The most effective material is high mass and flexible, like cork or hemp crete.

Those materials work by providing a physical barrier. This invention is not comparable because it appears to allow air to flow down the pipe but (somewhat) prevents the sound. I guess it should be compared to the performance of acoustic ducting or inline silencers (ie like in a car exhaust).

[tmikaeld]

That's why i mentioned bass-traps, which can be done with cheap PVC pipes in the corners of a room.

[abainbridge]

I still don't understand your point. In the scenario in the article, you've got some noise coming down a pipe and the invention attenuates it. By "PVC pipes in the corner of a room", it seems like you are talking about a way to remove resonant frequencies from a room - as some folks do to improve the acoustics of a room for a hi-fi setup. In the scenario in the article, the noise is in a pipe, not in a room.

[tmikaeld]

I noticed that people assumed that this invention could block any sound, but it can only block specific frequencies, so that's why i pointed out that low frequencies can't be blocked - the test itself doesn't mention low frequencies.

It wasn't a complaint to the invention itself, which is certainly promising for blocking sounds in ventilation while keeping airflow.

PVC pipes trap low frequency sound by eating up it's energy and since low frequencies penetrate solid objects, resonant sound is what people are most annoyed by and those are reproduced in corners of a room - which is a good target for PVC bass traps to cancel out the bass.

When it comes to high frequencies, they bounce easier, so it's more about building a "maze" of surfaces for the sound to bounce on until it looses it's energy, which seems to be exactly what they do in the article, they keep bouncing the waves backwards until they die out and it's quite clever.

[posterboy]

My thought exactly. The problem with low frequencies is the large wavelength. The size of the damper needs to be roughly proportional to the frequency for reasons I don't remember.

If I had to guess I'd say that standing waves don't leave the chamber.

It will also capture only a limited volume.

> The mathematically designed, 3D-printed acoustic metamaterial is shaped in such a way that it sends incoming sounds back to where they came from, Ghaffarivardavagh and Zhang say.

That's certainly not what a sound engineer wants. The usecases are a little different, containing noise in an MRI machine (which has low freq rumbles) or away from ground for a drone. The word droning sound is probably not a chance homophone.

They can scale the structure as needed, so potentially for low frequs, and fit many next to each other to form a wall.

The helical structure in the ring is like a long winded pipe I guess? It's literally analogue to an electronic low pass filter from an inductor in series between source and ground, without a recipient. What a sound studio needs instead is a capacitor to ground in parallel to the recipient.

[hatsunearu]

I'd need to some more research material to confirm this but I wanna say that the structure seems to exploit some effects that you can't reason with lumped model + T-line models.

[vonseel]

In what world is anyone using PVC to make bass traps? Every advice I have seen uses rockwool or something like Owens Corning 703/705. I am assuming you are not referring to the structure used to contain the acoustic material.