Unfortunately I don't know enough physics to offer any criticism beyond amiring the sheer awesomeness of the concept.
I respectfully request that this device be manufactured, mass produced, and sold on the xkcd site.
One more vote on that front.
Another spin on the comic that makes man-in-hat ever more the bamf: he's not the one operating the machine. He tells the other guy to operate all the switches for him. If his neighbors accuse him of using a device to destroy their amps and annoy them with undecipherable latin music, he'll now have the defense that he literally didn't do it.
In fact, he would be charged with aiding and abetting and end up with the same punishment as the guy with his hand on the button. Sorry.
And speaking of the law...
I so want one of those. The punk-ass neighbor kid likes to have sex with his gf in his car with the bass turned up to cover up the noise at like 1AM. This would eloquently solve my problem of bass waking me up...
While kudos to getting the guy to move somewhere else with creative car, erm, detailing, let's say, you also have the option of sending the police to say hello (way to ruin the mood) since I don't think that there is a region in existance without noise laws that come into effect around 11pm (sometimes sooner!)
My most amusing experience with this (and living across the street from a movie rental local means lots of idling cars with blasting stereos while buddy picks out a movie) was meandering down from my apartment in pjs, boots and coat, to tap on the window next to buddy's girlfriend who had been left in the car. The look of shock on her face as I let her know that the music could be heard three flights up was almost
worth the 15 minutes I'd spent fuming in my bed. Well, not really, but I find it easier to accept people who are stupid (i.e. don't realise what they are doing) over people who are assholes since informing the stupid people at least has the chance of being about change...and you can always hope that they end up receiving a Darwin award.