Uh-oh, @PapaLeo, we’re supposed to let the serious answers go first.
@mattbrowne, I think that’s too simple. There’s also a cultural and “politeness” override, I think. We don’t all just let loose. Efforts to suppress or contain produce different results.
Also there are the kinds of sneezes to consider (nose tickle, full cannon from deep in the lungs, etc..) and how clear or obstructed the nasal passages are at the time. I think the person’s vocal structures play a role. Not to mention habit. And what causes the sneeze in the first place: a virus, a little irritation from dust or mold, or something else. I think allergy sneezes feel different from cold sneezes, too.
I think sneezing is one of the funniest things we do. I have done so very much of it myself, as a child plagued by allergies and frequent colds into adulthood, that I am practically a connoisseur. I think I could create scientific categories of sneezes and describe them. Or has that already been done?