The social environments most people call "echo chambers" map entirely incorrectly to the metaphor of acoustic physics, whereas true "echo chambers" have the structure of something like a large cathedral...
...true sound absorption/anti-echo materials in contrast by definition include highly manifold structures with many internal divisions.
How does acoustic foam work? All we have to do to understand how does acoustic foam works is to look at the individual cell structure of the foam. You can see that the cell structure is open or porous in nature. This cell structure type allows for air to flow into the foam and enter the individual cells. Once it is in the cells, it moves around and this movement creates friction. We all know that friction can produce heat. If you have ever rubbed sticks together when camping to create a fire, you realize how friction works. Once the friction starts to produce heat, an energy transformation occurs. We do not lose energy, we change its form to heat.
https://www.acousticfields.com/how-does-acoustic-foam-work/
It is well known that the acoustic absorption capacity depends on the acoustic porosity content (open porosity). Indeed, scientists have focused on materials with interconnected porosity, especially foams made from polyurethane [1], [2], [3], [4], [5], [6], [7], [8]. It is essential to determine parameters such as the airflow resistivity, tortuosity and acoustic porosity to understand acoustic phenomena.
https://www.sciencedirect.com/science/article/abs/pii/S0167577X14000779
this is a structure that deadens echos
I think it depends on the type of sound: a canyon echoes shouts, while a cathedral echoes sermons. But a canyon won’t echo regular speaking voices like a cathedral does, and I think that’s what the metaphor is drawing on: the cathedral is an echo chamber relative to an open public square.
...because a Cathedral echoes more than a Canyon does! Which is my point! When people apply the metaphor of the echo chamber they almost always use it in precisely the incorrect mapping and speak of mitigating the "echo chamber effect" by creating large, enclosed spaces with huge unbroken internal voids where even whispers cascade all the way across the volume in a cacophony.
Conversely when people speak of systems of communication that are most like open celled or closed celled acoustic foam with many smaller spaces separated by manifold barriers and divisions, they are likely to refer to it as being prone to the "echo chamber effect" and I think it seriously hurts rational thinking on the subject.
I have never seen someone criticize a human communication system with the structure of a Cathedral as an "echo chamber" while gesturing to the structure of a Canyon as superior in that it lets echoes proliferate but doesn't concentrate them. Rather, it seems to be used almost without exception to argue in favor of making systems MORE like a Cathedral and less like acoustic deadening foam in structure.