raise you hand if you can still hear 40Khz

[Filliam H. Muffman]

I used to be able to hear to about 21 kHz. Walking into stores with ultrasound motion detectors made my teeth itch. When I was 24, I returned three TVs because the flyback transformer noise made me uncomfortable. I ended up with one of the last Mitsubishi models made in Japan. I don't know if it was better quality construction of the electronics or the hefty wood cabinet damped the noise to make it acceptable.

Working in a loud industrial plant for 10 years ended that even with wearing earplugs most of the time. Coming up on 30 years later, I am on the border of needing hearing aids.