So I'm out for a 73 mile ride this afternoon, and my route takes me through Boulder. I'm heading North out of town on Broadway hugging the edge of the street when it turns into a right-turn lane. Normally I take the lane in this situation and then hug the left-hand edge to avoid getting right-hooked, but I wasn't quick enough and am overtaken by an SUV wanting to make a right-turn. So I get on the brakes and start to swing in behind it.
Suddenly, the air is filled with a strange, piercing sound that scares the bejeezus out of me and startles the SUV driver so they abruptly hit the brakes, causing me to hit the brakes to keep from rear-ending it. A split-second later another cyclist overtakes both of us, swinging around and passing us on the left.
The sound was the cyclist alerting us of his presence...by yodeling...at a volume I never thought humanly possible.
So if anyone knows a tall dude in Boulder that rides in blue/white jersey & shorts, give him my compliments on his yodeling skill and lung-power.