When you say "ANY", do you really mean "any" or "any of yours"? You'll have to excuse me, but when I hear "audio app" I automatically think of Radio Paradise (because I'm the developer). Does it work?
My guess would be that you can't access the public IP address from within the local network - it's a router issue. I don't know if I'm saying that right, but I have the same problem when I'm testing URLs with my domain name from my local network. I don't know exactly what the issue is (I'm no networking expert), but I kind of solved it by putting an entry in my router's host table to map my domain name to a local IP address.
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