I enjoyed this article and having had roosters crowing in my house about 3 meters away from my bed I know how loud they can be.
I measured the decibel level at Im away with a condensing microphone and I got readings of around 100db. Different roosters produced different loudness.
A point worth mentioning in your article is that hearing damage is not just dependent on loudness, or decibel level, exposure time to that level is an important factor regarding permenant hearing damage. Of course, at a few meters away the loudness declines so distance from sound source is also a factor.
I found I could sleep through a roosters morning crowing using ear plugs that gave a 35db reduction in decibel level.