Found it!

This has been bugging me for years. I remember watching this PSA on tv in the 1970s, probably even the early 1980s. For the longest I couldn't think of exactly what the commercial was about but I knew it was some PSA. After a bit of searching, I found it on Youtube. Apparently, it's from the late 1960s about preventing forrest fires.

Mosquito Tone

I thought it was the new TV on the fritz, but apparently, this is something that's been used in television commercials in recent years. The net has all the info about this KFC ad where a 'mosquito tone' is used. They say only young people can hear it but I can hear it and I'm not young and on top of that I hear these so called mosquito tones throughout many if not every commercial break. At least the tv is ok and this is normal, but I wish they were never used. It's quite annoying.