I d just like to chime in that I experienced these things on several occasions in Tokyo and I d like to voice my vehement opposition to them They re not annoying they re debilitating Everything mentioned in The Mosquito Health effects should be taken seriously it s not simply a noise it s a pulsing Something like this Bang loud quickly fades out and then repeats probably 2 3 times per second When I came across them it went straight to my inner ear and made me disoriented within seconds and physically nauseous within a minute of exposure The fact that it emits at up to 94 decibels to me should make it highly controversial At 85 dB OSHA requires hearing protection in a factory 94 decibels is louder than a lawnmower and these speakers are usually stuck run above your head on sidewalks To some of the previous comments in this article to me The Mosquito less of an anti loitering machine and more of a military sound weapon It is truly that bad imagine an instant pulsing ear infection simply because you walked past a department store that doesn t want kids loitering about Just my 2 cents talk contribs