I’m curious, how many people are aware of these sounds. I have designed, etched, and built my own switching power supplies along with winding my own transformers. I am aware of the source of the noise. So, does anyone else hear these high frequency sounds regularly?
Could you be hearing the Hum?
Edit. This article implies that people can’t hear it, but many people can, and, while it causes a mild annoyance with most of those that can hear it, it has caused severe disturbances in others.