Clicking the play button below will produce a tone that is generally only heard by people under the age of 25. It has been used as a deterrent device to keep teenagers from loitering in malls and shops, and sounds similar to a buzzing mosquito. The elderly and people with hearing damage often cannot hear the sound
you can find the button here (open the site below)
ps: i ment teenager
you can find the button here (open the site below)
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ps: i ment teenager