I was in New York recently and the Franklin Av Shuttle subway station seemed to have these devices throughout the station (entry hall, stairs and platform were

I was in New York recently and the Franklin Av Shuttle subway station seemed to have these devices throughout the station (entry hall, stairs and platform were all covered). Also in my 20s and I could hear them clearly - the frequency was changing between several very annoying ones, all in the extremely high pitched spectrum (17.5-20kHz, from what I read online). By the time the train arrived I was really glad to get out of there, it made my head hurt quite a bit. It was an awful experience. Apparently the MTA decided that royally annoying young customers was less important than preventing loitering kids.