The FTC warns people about those stupid ultrasonic controllers for pests - we know they are bad we see it all the time but people just don't get it.Here is the link to the new webpage where this warning sits. It is from 2001 - but still true. The website was redone and the old page was gone - this is the new URL for this warning.
If you know someone who wants a little more proof that these things are essentially a waste of money, here it is!

https://www.ftc.gov/news-events/pres...c-pest-control

Cheers~