Also when out the back it's often possible to hear the Eurostar go through as well, even though that is 2.5 miles away, and the other side of the M20. quite a distinctive sound on that one!
You said that it is distinctive, but is it any more or less annoying than the M20? I am about 1 mile from the M4, but although I can hear it on a quiet night when the window is open, I cannot say it annoys me. Equally I can faintly hear the
GW▸ main line but it is further away and less noticeable. The M4 is much more noticeable in damp weather.