I've seen people on the T cringe like mad when a child laughs,

That's because children giggling is the harbinger of children shrieking, either in delight or because something flipped the Random Mood Switch and they're now screaming because they're upset. Plus there's the Moo factor so commonly encountered in public places - A mother acting like everyone else should accomodate her child's publicly unacceptable behavior, or that everything her precious child does is sunshine and roses, regardless of how obnoxious her brat actually is.

I'd much rather listen to mechanical noises than the hair-raising sound of a nearby sprog any day.