If this were a sane society we wouldn't need squeakers to keep track of children because they'd be making enough giggles and other happy noises to keep track of them. Also there'd be no chance of these noises being drowned out by machinery.

Of course if we were a sane society people wouldn't react to the sounds of children's happiness as though it were fingernails on chalkboard.

For God's sake, I've seen people on the T cringe like mad when a child laughs, all the while happily enduring the ungodly mechanical shriek of the train as it scrapes around the bend towards the station... something's wrong with this picture.