Somewhat off-topic, but this horn looks interesting and not that much more expensive than an air-zound:

That's battery operated, which isn't terrible, but I like having the air powered Airzound. I top up my tires every sunday night for the week's commute, then just hook up the pump to the Airzound and check the pressure there too. I've already got enough things on rechargeable batteries that adding a Hornit wouldn't be that bad, though.

BTW, the psi rating on Airzounds is now 80 psi, so maybe they last longer? I've had mine since about may or June and use it pretty regularly on my commute. I'd say about 50/50 on vehicles/pedestrians.

I noticed that when I bought my most recent one. I've still been pumping mine up to 120 PSI. It's been fine for, well I guess two years now come March. The only time its been at less than 120 PSI during that time is when it gets used, even on my worst day commuting I don't think it got down to 80 PSI before getting recharged within 24 hours or so.

I really doubt they changed the design any, I suspect there are a few locales where the amount of decibels it puts out at 120 PSI make it illegal, so they downgraded the rating on the packaging.