So? Is any artifact that happens to be used in the commission of a misdemeanor automatically forfeit?
If someone's music is too loud, give them a ticket. If they lose in court and don't pay the ticket, then impound their vehicle. Impounding the vehicle first means that even if the people win in court they're still out the towing and bailment fees (which is, of course, probably the goal). As one opposed to punishing people before they're found guilty, I find this abhorrent.
Who says it's automatic? For a particular problem that has proven difficult to solve in a more conventional way, there's nothing wrong with doing this. It's not as if it is easy to accidentally get caught when you have to install special equipment to commit the crime in the first place. The folks who have committed no crime yet are constantly under assault by these mobile sound weapons have rights too. What's more abhorrent, the criminal behavior or reasonable measures to end it?