When I was in Florida last week I happened to sneeze in the car (allergic to Orlando) and a colleague told me that my sneezing is not authoritative enough - I'm an inadequate sneezer.
Since then, I have analyzed every sneeze, dissecting it for the right combination of depth, volume and inflection. My findings? Too deep, and everyone can tell you're trying too hard. If your sneeze contains too wide a range, i.e. too many different "sneeze tones," it sounds cartoonish. To date, I have not found a disadvantage to high volume - everyone loves a really loud sneeze.
It is very difficult to change your sneeze at 28, but not impossible. With the support and constant nitpicking of my friends and co-workers, I'll get there. Pass the tissues.