AirZound is supposed to be awesomely loud. You can find some reviews of it online. Reviewers suggest caution using it around pedestrians because it is so loud it might give someone a heart attack. But it gets drivers' attention because it sounds like a tractor trailer. You pump it up with your pump.

I would like to have had one yesterday. I was proceeding along a 4-lane street, no traffic, riding to the right side of the right lane about 17-18 mph like a good boy when some jerk comes up behind honks his horn angrily a couple of times then finally zooms past. Needless to say, I was VERY impressed that his piece of crap little Toyota pickup truck could go faster than an old fat guy on a bike. After he passed I checked behind me. There wasn't a car in sight. He could have easily and smoothly gone around me but CHOSE to be an a__hole. Luckily such things happen so seldom I am still amazed when they do. It takes a real loser to be impressed with himself for hassling a cyclist.
Whatever,
Raymond