http://imgur.com/UMrFawG
Hope picture is okay! I think its this add for the chance of winning a Apple product, that makes the sound, but Im not sure. Basicly, its been here for long time (2-3 months?) for me, and it goes "DUM DUM DUM, DUM DUM....." and cycles, really loudly with trompet sound. So annoying, and it comes up often. Would pay money to get ride off whatever the add that does it.
Sorry not an english add I got inn the picture, but its just a fake scame add anyway, so no important text missed.
Edit: Had it again now today, defiantly a common fake spame add.