Some comedian on TV was saying the same thing… “I’m stopped at light and a car pulls up beside be playing this song. Now it’s stuck in my head. Does anyone recognize it? It goes like this… thump-thump-thump-thump-thump…”
First, electromagnetic interference is frowned upon by the FCC. What may drown out car stereos will definitely interfere with quite a few other devices in the neighborhood. Sooner or later someone with enough IQ will drive by and think - “every time I get near this corner, I pick up interference”. You want your device to be intermittent or sound-triggered.
Second, unfortunately most of those obnoxious guys whose volume goes several dozen decibels beyond their IQ, are using CD (or mp3) players today. I heard of some college physics professor who had a device for getting rid of obnoxious radios at the beach, back in the days of transistor radios. That was easy. CD’s are designed as much as possible not to pick up outside interference.
Third, most electromagnetic power is not easily focussed into beams, except at thehigher (microwave and above) levels. One again, aiming high doses of microwaevs at people or out into the world in general is an FCC offense. For regular radio power, think of the EMP pulse signal as an expanding bubble. Therefore, at twice the distance, the surface area of the bubble is four times larger. 3x gives 9x, etc. Square law; so to generate a decent signal that can zap a device at say, 50 feet, you need a source signal that’s pretty darned strong, even if it isn’t a thermonuclear event. To zap a 500W speaker you would need one heckuva zap. On teh plus side, the newer electronics like CD or MP3 players use much more sensitive IC transistor electronics.
As a side note, there are “Cell Phone Range extender” devices for that odd corner of the building where the cell signal is too weak. they work by acting as a dumb repeater amplifying signals in and out of a pair of antennas. I’ve always wondered if you could create a cell phone jammer by making the function only go one way - boost the signal coming in from outdoors but not outward…
the Israelis were rumored to have a device to shut down electronic (electric) devices at a distance, that was used as part of the Entebbe raid. Of course, this rumor was back when the Israelis could do anything; the last Lebanon imbroglio has brought their reputation down to earth.