A coworker just announced with great excitement her new twins. She showed me ultrasound prints… you could see the forming bones and so on. Apparently the ultrasound display is live like video and she could see the twins moving and waving…
My question a little later is: can the developing babies hear ultrasound? I know that as we get older our ability to hear high frequencies above 20 000 Hz drops; does this hold in reverse as well? Can very young children hear sounds of, say, 40 000 Hz? And babies in the womb hear even higher? Would they hear the ultrasound?
As an aside, wouldn’t they be scared [PiG-13]-less by the lights and other photographic gear used to take those amazing in-the-womb pictures? I imagine it would look like the robots they explored the Titanic with…
The answer seems to lie in the word itself. Ultrasound, or the use of ultrasonic waves, is, by definition, in a range beyond human hearing. Of course, babies may have higher thresholds (i’m not an expert), but i can’t imagine that those who designed the ultrasound machine would have them use frequencies that might conceivably be heard by the foetus in the womb. Or, for that matter, by any dogs that might be in the area.
Your muscle strength decreases as you age. Does that mean that fetuses are super strong?
This is from a possibly-marginal site, but what it’s cited from a decent source: “Regarding the beginning of hearing, the ear starts to develop only a few weeks after conception. However, the auditory system of the brain really doesn’t function well, if at all, before about the 26th week, that is at the beginning of the last trimester of pregnancy.”
Podkayne, I’m not sure this is a question that can be dismissed out of hand like that. Our perception of sound depends on vibration of the eardrum and fluid in the cochlea. Since the body is growing rapidly at that time, it makes sense that the range of hearing will be getting lower and lower. Since the cochlea and eardrum are smaller in an unborn baby (obvious), then their resonant frequencies will be higher, right? If it’s half the size, they’ll hear an octave more, and so on.
Obviously I’m no doctor, but it seems like a reasonable observation…
It is also possible to percieve ultrasound through the sense of touch. Try sticking a finger into a sonicator bath of the type used to clean rings in jewellry stores. It sort of tingles a bit. Grabbing onto the probe of a sonicator used to disrupt tissues in the laboratory can be an extremely painful mistake.
