What can a fetus hear in the womb?

We've seen parents-to-be in sappy movies putting headphones or speakers up to the pregnant woman's stomach. Sometimes they're trying to make the fetus listen to some grandparent's voice. Sometimes they're trying to make some kind of crazy-smart super baby. But can a fetus stuck behind thick walls of flesh hear any of it? And if it can, would it hear anything more than muted noise?

First of all, parents-to-be need to be careful with that kind of stuff. The wrong kind of sound, especially low frequency vibrations, could turn a kid into a bony, muscled-over, dead-eyed drone. Some wasps determine what their larvae will develop into by drumming their antennae on the egg chambers, and studies show that young rats exposed to similar vibration lose fat and gain bone and muscle. But how about normal, high-pitched conversation? Surely a fetus couldn't hear anything like that.

Studies by the US Navy say yes they can. Obviously, the Navy couldn't experiment on actual human fetuses, but they could and did play around with lamb fetuses. While the fetuses were in development, the Navy placed tiny microphones inside of the lambs' ears. They then placed microphones in the fluid around the lamb. A final set of microphones was attached to the outside of the sheep. Once the microphones were in place and recording, the Navy used speakers to play a series of words to the sheep. The sheep were unmoved, but a group of volunteers listened to the recordings that the three microphones made. The volunteers were able to understand all of what was recorded on the external microphone, three-quarters of what was recorded on the microphone inside the sheep, and 30-40% of what was recorded on the microphone inside the lambs' ears.

I know that this will spur a great deal of potential parents to record obscenities and try to get the Guinness world record on the youngest person to say f***. Before you do so, however, I must remind you that this study was made possible by the United State Navy. And if there is one thing the Navy disapproves of, it's salty language. I trust you will do your duty.

Via The Naked Scientists.