Not sure about your math there at the end. I believe the 0.4 dB at 3000 ft, but I think it would remain constant all the way down.
Most human better be able to tell the difference between 2 events that have 3 dB difference or they need to get their ears checked.
I agree with you though, the reduction gained for the increased risk of buying the street if you run over is not worth it. Me suspects there is more to this than meets the eye.
