like burgler alarms? 100 db at 20 KHZ would be inaudible to men over 22 or so. Kids would object though.Not good if people can hear it. That reminds me of that recent inventiion from Britain to rid of young hooligans from storefronts.The adults couldnt hear it but the teenagers would scram. Kinda mean when I think of it. Something mean old men would think up.
Dennis
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