So the teen repellent sound used by shopkeepers in England has been turned to advantage. The best article I’ve found on it is from National Public Radio. Inventor Howard Stapleton, creator of the Mosquito teen repellent, says only a few people over age 30 can hear the Mosquito’s sound.

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29 September 2006, 4:52 am
I didn’t hear a thing. Speakers are good. Age 37.
10 January 2007, 1:31 am
I’m 21, and owwwwie, that kinda pierces my eardrums. I gotta admit this is fascinating
10 January 2007, 2:32 am
I’m 37 and I could hear it fine, but it didn’t really annoy me all that much.
09 February 2007, 10:53 pm
I’m 44 and heard it after turning my volume up a bit - a colleague 1 year older, could not.
19 February 2007, 5:48 pm
I’m 14.
Oww. That sound hurts…
17 March 2007, 10:30 am
I am 40 and I can hear it just fine. Very annoying.
26 March 2007, 3:51 pm
I’m 49 and can’t hear it, darnit. My daughter, 28, hears it clearly and said it’s annoying. My dogs heard it, too. Interesting. I wonder what else I’m missing out on. =)
19 November 2007, 3:24 am
Oh wow… I tried to record it on my phone… but suprisingly, my phone could’nt record it. But my ears still are pierced. But i guess they should be… since I’m only 13
29 May 2009, 12:06 pm
Wow! This is wierd! My husband and I both sat here and listened to the sound. I heard it loud and clear at its lowest setting, but my husband did not hear a thing. He is 59 years and I am 55. Strange….
19 June 2009, 9:42 am
I heard it…..It is almost as bad as a marker on the whiteboard. I am 49