[lotharcable2]

It is generally said that the lowest threshold for people to perceive time delays is around 10-15ms.

Speed of sounds is roughly 343 meters per second. Which means translates we can sense the delay difference of about 4-8 meters or so.

Which 100% corresponds with what you are saying. 20 meters is a 58ms-ish delay.

A 200ms is about 70 meters. Which would be like having conversation between people using one of those accidental sound projection features that sometimes happens with large open buildings like sports stadiums.

people talk in a cadence of around 100-200 words per minute. I guess we could say that is 300-600 syllables per minute. So that is about 200-100ms per syllable.

It all kinda lines up.