Just learned that Lewsitown, Pennyslvania still operates their curfew horn
at 10 p.m.
I used to hear it in the late 50's early 60's when visiting my grandmother.
What I remember was a strange: BEEEEEEEEEP....arrUUgah, BEEEEEEEEEP....arrUUgah, ..... arruugah.
Was last arrUUgah an echo?
Now I believe the "arruugah" was residual pressure leaking off.