To the above review.

No, you are not supposed to hear it, though some humans can, normally in early years as late as teens. I, for example, can hear most frequencies, but not all. The most likely reason why you cant hear it now, after the update, is because they probably adjusted the frequencies to make them either more effective or less apparent to humans.

I have used things like this before, so I will give this ***** before its even finished downloading ;), because everyone should know about it.

Nathan Lamarche about Anti Mosquito + Free, v1.1