ORIGINAL: perreback
That's specifically a vowel *sound*. That's why we write ''a young man'', ''a university'', ''an hour'', ''an heir''. And I suspect a lot of you Americans write ''an herb'' as well.
Does anyone know where the permission to drop the "H" sound from the beginning of a word comes from? I was raised to believe that herb was pronounced "erb" and that vehicle was pronounced "veicle." There seems to exist no rule in the English language for it. It appears to me to be a holdover from a bad lower class English accent.