The U.S. military has gotten serious:
The US military has acquired an arsenal of "sonic bullets" for use as non-lethal weapons. One plays backward the sound of a baby crying at 140 decibels, well above the threshold of pain.
From the FT’s review of the new book Manifesto for Silence, which says silence is a crucial and threatened commodity.
I wonder why it’s with a baby crying backward? In any event, I have a hard time keeping my sanity when just one baby cries at a normal level on an airplane.
I find crying babies MUCH less annoying than loudmouthed kids and adults, who should know better. One I’d like to hold and soothe, the others I’d like to hold and bruise.
Crying babies have a mean frequency at 1kHz, which is easily heard by the human ear. 1kHz is also used for most alarm systems as people can hear it from a far distance.
I guess thats why they chose crying babies for sonic bullets…
Less-lethal
http://www.defensetech.org/archives/cat_lesslethal.html
Non-Lethal Weapons
http://www.defenseindustrydaily.com/cat/ordnance-guns/nonlethal-weapons/
They use a baby’s voice backwards because the decibel level goes up in backwards format. It increases by an order of magnitude.
The World Health Organization has this to say about noise:
“The potential health effects of community noise include hearing impairment; startle and defense reactions; aural pain; ear discomfort speech interference; sleep disturbance; cardiovascular effects; performance reduction; and annoyance responses.”
Read more at:
http://www.who.int/docstore/peh/noise/Comnoise6.htm