First of all, you should not be scared of the virus warning. Its a good thing. (well, as long as its not a FP) It means Avast! did its job. It is rarely sign of some epic system-wide infection, unless it keeps happening many times.
But it is the same sound, played 1 vs. 3 times, I see what you mean, I guess thats not...."optimal".
But as long as they don't bring the old Avast! air-raid siren back again, I'm happy the way it is, jmo.