I keep hearing similar high pitched sounds in Tokyo in front of some stores as well, so the statement that only people up to 25 years old can hear it sounds incorrect.

The Mosquito youth repellent has even won an Ig Nobel prize: https://www.theguardian.com/uk/2006/oct/06/science.higheredu...

I think this fits the general trend of making urban architecture more and more hostile to the public.