16.5kHz acoustic anti-vandal system at the fountain

Hauptplatz, Graz - 16.5kHz acoustic anti-vandal system at the fountain. Installed by local authorities there is a sonic anti-vandal system running at the fountain on Graz Hauptplatz. It consists of several small speakers which are constantly emitting high frequency impulses of around 16.500 Hz. Do you hear it? As we grow older, we tend to loose the ability to hear those high frequencies. Therefore, anti-vandal-systems such as this - a similar model is the better known Mosquito MK4 - are intended to affect teenagers in particular. The annoying sound is supposed to drive them away. However, this particular device seems to be quite ineffective. When I got there, there were several teenagers hanging around at the fountain. Even if they heard it, they said that they weren't bothered by the sound. Please note that audibility of this sound may also differ depending on what playback system you use! Laptop speakers are not the best option. [Recorded with Hi-MD-recorder Sony MZ-NH900 and external microphone Beyerdynamic MCE 82]