Noisy restaurants are no accident. Young people (who spend money) supposedly like places that feel "alive."  Old people (who don't spend as much) hate noisy places and won't go.  So, restaurants who want to fill up their tables on a Saturday night with young people drinking $12 martinis play loud music and avoid sound dampening decorations.<p>I'm not suggesting that the Cone of Silence wouldn't be a good thing -- I'd buy one!  However, the way to attack the problem is social rather than technological.  Imagine starting a grass-roots campaign to tell restaurant owners/managers that you hate how noisy their establishments are.  Print stickers that say, "I wish this restaurant was more quiet" that could be stuck on credit card receipts so management would be forced to hear your message.  There's no business model in this, though.