The sound of a baby struggling for breath with whooping cough is as distressing as it is distinctive.

BBC: Whooping cough makes a comeback

Among the other options 4moms is considering is a sound system, and perhaps a heating element to keep baby toasty on even the most frigid days.

WSJ: Cutting Edge, for Baby

It involves an instrument sending a sound into the baby's ear and measuring the level of returned sound which calculates the level of hearing function.

BBC: Babies' hearing problems undiagnosed

It is not the keening and caterwauling I mind so much as the eerily human nature of the plangent cries, which can sound like anything from a baby crying to a couple of nightclub bouncers fighting in an alley.

BBC: The lairy, wary cats stalking Jerusalem bins

What had tried to kill him was not just in the pond but out here, too, in every natural thing, and there was no him, no Suzanne, no Mom, no nothing, just the sound of some kid crying like a terrified baby.

NEWYORKER: Tenth of December

The more traditional method of measuring hearing loss, the distraction test, requires a baby to sit upright on the mother's lap, responding to sound without seeing the source, and therefore cannot be done before 8 months.

BBC: Babies' hearing problems undiagnosed