If I ever bought a gun, those G*dd**n M****rf*****g things would be my first targets…

Note that sustained exposure to 90 dB may cause permanent hearing damage, is similar in loudness to truck traffic, and is louder than a lawnmower. 85 dB is when OSHA requires hearing protection in factories. And they stick those speakers usually just overhead on a walkway.

http://en.wikipedia.org/wiki/The_Mosquito#Health_effects
“…the ultrasound affects not only hearing. Disruption of the equilibrium senses, as well as other extra-aural effects are well known. With the sound levels that can be reached by the device, the onset of dizziness, headache, nausea and impairment is to be expected. This is not the limit of the total risks to safety and health.”

Firstly, 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. Also, I don’t know at how many decibels those things shoot out their god-forsaken noise, but it goes straight to my inner ear and made me disoriented and physically nauseous within a minute or so of exposure.

It’s less of an anti-loitering machine and more of a military sound-weapon. I’m not totally against the idea, just make the things emit a solid square wave and TURN DOWN THE DECIBELS. It felt like the sound waves coming out were pressure waves. The things as they are need to be fucking outlawed, they’re HORRIBLE.