Listening with iPod while sleeping?

[Shannon]

I just set my lappy playing and loop it. Clears the whole room. 24/7.

Yepp, I ventured into that zone I was somewhat nervous, but luckily the laptop didn't heat up and no problems. However, sadly I have no idea of the frequency of the speakers and don't know how to check.

However, I've just received iPhone 4, to my huge surprise, and I am wondering if it's possible to just use them; the Wikipedia page indicated that the frequency is just right, but sadly it lacks citation

If you can play ultrasonics on your laptop, you will hear them as a high pitched squeal only at the maximum volume, or for speakers that can barely handle it, you'll start hearing speaker distortion when you get close to max, but you should be able to hear nothing (or close to it) while playing them at a normal volume. If you speakers can't handle it, you'll hear scratchy voices, static or such even at a relatively low volume.