It appears you only check for blocks to be opaque?

Which makes building with slabs or windows hard, since those are detected as basically open space even when they aren't ^^"

Not really sure if there is a good way to detect spaces other than that though, especially ones that are computationally feasible. I guess one idea would be to try and "flood fill" in another thread until it hits a max block count and stops trying, or finds an enclosed space. Then it could store that space for later usage or something, but no clue.

This detection is about performance. AmbientSounds should not have a noticeable impact. Furthermore I don't think it's important to be accurate.

I could treat slabs and windows as walls if you think that improves the detection?

I will close this issue for now, but I'm still waiting for a reply to my question.

Sorry for the late reply. I feel like maybe a config on which blocks are "blocking" may help, then you could set e.g. glass blocks to block sound despite being non-opaque. But just adding them in fixed would help too I suppose. Stairs too if they aren't.

It's released now.