[Mercat]

I carry one of those devices that scream loudly if you push the button. And I carry earplugs. Put in the earplugs, roll the window down a tiny bit (they’re small) push the button and toss it outside. Anyone ever use one?

[ProtectOurFreedom]

That's a darn good idea. You can buy similar piezo-electric "screamers" for your home security system. The sound is so loud and awful, the burglars will be scrambling to leave your home. I've tested one for home security and it was incredible. I would dread having that going off in the car with me next to it, but the earplugs idea is good, too. Keep some of the screamers and foam earplugs in a baggy in the car console ready to go just in case.

KOSIN Safe Sound Personal Alarm, 6 Pack 140DB Personal Security Alarm Keychain with LED Lights, Emergency Safety Alarm for Women, Men, Children, Elderly

140 dB is quite loud.