I use one of these. It is plenty loud enough for people who are not wearing headphones to hear at a decent distance. No bell will be loud enough for those who are wearing headphones, nothing short of an air horn is loud enough for them and even then if they have the volume cranked.... So I give Mr and Ms iPod as wide a berth as possible and if my sudden appearance in their peripheral vision as I pass causes them to soil their pants, it does. I don't think there is anything that can be done for them if you don't want to carry an air horn. Mostly I think you buy a bell based on style, some are louder than others but not enough so to make a significant difference very often. Richard, a bell is of no use at all in warning cars, for them you do need an air horn.

Ken