I have used air-zounds in the past, but they died on me.
I've used a 12 volt car horn, but the darn thing draws too many amps.
I now use a 12 volt 115 decibel piezo alarm, with a toggle switch on my fairing.It sounds like a truck's back-up beeper, so it gets attention.
I use a bell to let the pedestrians know I'm there.
One of my bikes has a bulb-horn, which is not an air-horn in the sense of a Zounds Eco-Blast.
So I put "other" down in the survey.