Not very good, IMHO.
Nashville has 70 of these devices located around the city.
There's one at a school about 1/2 mile from my house. Some test days(1st Saturday at noon) I've never heard it. Others faintly; have only heard it loudly enough to recognize if atmospheric conditions are right or wind is blowing this way.
There's another ATI at school about 3 blocks from the church where I am organist. I mentioned this on another ATI post. Two weeks ago I stopped practicing a couple minutes before noon so I could listen for the test.
My "headquarters" is near front of sanctuary on side facing the school. I heard the siren. However, if it had been sounded on a Sunday, I doubt that it would have been heard in that area.even if I weren't playing.
The Nashville ATIs just sound like a high pitched electronic squeal. I've never heard a "startup" or "winddown" from them.