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
Go out to a field and try to produce an echo. They literally require walls to bounce off of.
You need some space yes, ideally the inside of your chamber needs to be mostly empty and insubstantive.
However, echo chambers can not be filled with too much space, because echoes don't work at infinite scale. Sound dissipates and loses energy as it travels through air, so for an echo to occur and you to hear it, you need to be a relatively short distance away from a wall. To be truly echoey and hear multiple echoes of the same sound bouncing back and forth on the walls in front of and behind you, you need those walls even closer together, for not just the extra distance travelled, but also how much energy is lost during each reflection.
It is not that act of reflecting off a surface that induces an echo with energy, the echo is a transformation.
The same dissipation of energy occurs no matter what because of air friction, what sound deadening structures such as acoustic foam do is increase that friction per unit of space.
The background effect of sound slowly losing energy simply from being conveyed through the air represents a minimum sound deadening capacity in terms of space not a maximum.
Reflection doesn't induce energy, it dissipates it because it does not reflect perfectly.