Staying recently in a South Yorkshire town called Rotherham—described in one guidebook as “murky,” an inadequate word for the place—I was interested to read in the local newspaper how the proprietors of some stores are preventing hooligans from gathering outside to intimidate and rob customers. They play Bach over loudspeakers, and this disperses the youths in short order; they flee the way Count Dracula fled before holy water, garlic flowers, and crucifixes. The proprietors had previously tried a high-pitched noise generator whose mosquito-like whine only those younger than 20 could detect. This method, too, proved effective, but the owners abandoned...