Use a horn. The Honk-a-Hooter is the size of a bell. My "train" (tandem+trailercycle) has a larger horn. Americans know a horn mean get out of the way from the overuse and abuse of the automobile.

I don't believe you are answering the question. I believe the OP was seeking an effective but polite/non-confrontational method of announcing his approach prior to passing a pedestrian. Your answer appears to be to a method for rudely prompting pedestrians to "get out of the way."

I use a bell when I am on the trails, towpaths, and open rides. If people get scared, they should probably lower the volume on their I-pods.

You know, there might be a problem hidden in here. As cyclists, we are taught to ride on the right and pass left, just like any other vehicles. Pedestrians are taught to walk on the left, facing traffic. Those general rules open some interesting possibilities, especially when rounding blind turns.

Get an airhorn from a boating store.they are palmsize and use a small air canister.No really,a small bell that tings always seems to work.

The problem with "On your left" is that the pedestrians didn't know you were coming and have only a few seconds to process what's going on. They don't encounter enough cyclists to have an automatic reaction so their reaction will be unpredictable (by the time their mind has processed "left" you're already there). So I ring my bell once or twice and slow down, they may go left, right or split but they understand they need to get out of the way. It seems to work very well in most cases. (And then I say "Thank you!" as I go past).

There's a time and place where even dinging a bell is unnecessarily, well, "insistent", if that's the right word.

What I'm thinking of are places like down by the reflecting pool between the Lincoln Memorial and Washington Monument, where everyone is guided onto the walkways between posts and chains (which I don't mind; otherwise, everyone would walk everywhere and trample the grass into dust). One time when I was down there at the Lincoln end near the Vietnam Memorial, a cycling couple was approaching the walkway intersection, ding-ding-dinging over and over, hoping that the families wandering around would step aside to let them through.

Now, I don't mind announcing one's presence, and understand that we don't want someone to accidentally step right in front of a moving cyclist -- but, honestly, was it necessary to flick their dingers so much? Were these riders in enough of a hurry on their Sunday cruise that they couldn't chill out, slow down, and pick their way through at a slow walking pace?

MUPs are one thing, open streets are another (I once called out to a lady wandering into the street, "Whoa, whoa, traffic, traffic!" so that she wouldn't get hit by the cars coming behind me), but c'mon, don't be That Cyclist. Unless you're an ambulance or a cop, there's no reason to force your way through a crowd. And if you're trying to maintain a certain speed for the sake of exercise, you really need to find a less-crowded area, or at least a better time of day.