When I was younger I messed with a signal generator, and noticed I had a drop out in my hearing at precisely 15.5KHz. Apparently this is caused by being exposed to TV sets - the noise they make actually damages your hearing at that frequency!<br>At age 36 I can no longer hear the noise of a CRT at all unless I put my ear very close to it. I can hear the morse code at the end of the video, but only if I use headphones and turn it up really loud.