Some have suggested that a bell is better than a shouted warning, partly because it's audible from farther away. What kind of warning is the right one? Do you find that "on your left" actually lead many people to move left instead of watching out to the left?
There seems to be significant differences of opinion on what kind of audible warning a cyclist should give.
In my personal experience "on your left" only works if I am overtaking a cyclist who is traveling just slightly slower me. If the speed difference is more then 5 mph I have to yell "on your left" louder and earlier. This seems to change the interpretation from a safety warning to a "get out of my way" command.
My commute from Lincoln Square to McCormick place varies by time of day and day of week. Sometimes I use my race bike, or a cx bike while dressed in kit and other days I will ride my cx or single speed dressed in cargo shorts or jeans. I find the perception of "on your left" will vary more to my dress then to my style of riding.
I also use the "on your left" method only to people who I am overtaking and they seem to be drifting left or not holding their line unpredictably. Personally I find no need to announce an intended pass to a jogger or other cyclist who seem to be traveling in predictable manor. I also look to see what they will be encountering during the time I will be passing (road hazards, will they be overtaking another)
All this of course is assuming that they can actually hear you, almost all joggers wear headphones and even though I believe it is illegal in Chicago, too many cyclists also wear them.
Of course, your courtesy is all a big waste of time when you close in on the person you're passing only to see they're sporting earbud headphones....
On the other hand, I was approached by an older gentleman who complained that I wasn't courteous and deferential enough to him when I was entering the Oak Leaf Trail near my home. I found that if I ask "May I please pass on your left, I get a more positive response.
Unpopular opinion: The mighty standard "On yer left!" is unreliable, especially on mixed use trails. It works among experienced cyclists, is useless otherwise. Most people do not recognize the phrase; some make an instinctual guess and step to the left-yikes!
The word "passing!" creates an instant image of the scenario in the mind of anyone above driving age. Very effective, single word warning.
If I have doubts that they are licensed drivers (children, most likely), I use the word "bicycle!". Even if they are trail neophytes and unschooled in trail etiquette, this phrase induces a rapid recognition of the situation and the approaching hazard.
When its a group, there is added peril when they form multiple, conflicting reactions. Use "bicycle!".
"Bicycle!" works well with the dog walkers, too. They must anticipate and counter the animal's tendency to chase, so they appreciate this useful and clearcut early warning to them.
And yes, the ear buds and headphones are worn by people shirking their responsibilities to themselves, they cannot be helped.
I like (and I've said it before) "Bike Back" they use it in pelotons and has no directional bias except that I'm closing on you. Two hard sounds that can seem friendly, or barked like an order in an emergency.