It's quite true. Most people cannot see a computer monitor flicker if the refresh rate is set to 60hz, but it gives me a headache within a matter of minutes. Whenever I did tech support, the first thing I would do if the monitor was set to 60hz is change it to 70hz or higher. I didn't have to check the settings, I could easily tell from everything just barely flickering for me. Fortunately new LCD monitors don't havve the same problem, even if their refresh rate is 60hz, as the brightness of the pixel doesn't fade away.

Similarly, with the new LED products that are coming out that run on A/C power, depending on how the power is rectified, I can see the 60hz "pulse" of the power in the LEDs. Incandescent, fluorescent, or DC powered LEDs do not cause this problem for me.

Other examples are CRT televisions that produce high-pitch whines cannot often be heard by others, but drive me absolutely batty, and when I was on vacation in Tokyo, Japan there would sometimes be ultrasonic bug repellers near entrances to businesses to prevent bugs from flying in the open doors which would also cause me pain.

In all of these instances, some other people experienced the same problems, while most people didn't. Some people just aren't sensitive to such things, or aren't as receptive. It's crazy how no matter how hard of a time I have deciphering what a person is saying when there is a lot of noise, there's no way anybody could sneak up behind me unless there was loud music via headphones or speakers going on..