[liberationtech] LRAD counter-measures?

[Scott Elcomb]

Not a specialist at all but believe it's worth pointing out; live
prototyping (the second frame of the xkcd comic) against an LRAD in an
urban environment could prove dangerous:

"Noise cancellation at other locations is more difficult as the
three-dimensional wavefronts of the unwanted sound and the
cancellation signal could match and create alternating zones of
constructive and destructive interference, reducing noise in some
spots while /doubling/ noise in others." (emphasis mine)

http://en.wikipedia.org/wiki/Active_noise_control


Regarding the last two xkcd frames... I wasn't aware LRAD's could play
music (never thought about it tbh) but it sounds like they can:

http://en.wikipedia.org/wiki/Long_Range_Acoustic_Device#Whaling


On Sun, Dec 14, 2014 at 6:05 PM, Jay Cassano <jay at jcassano.net> wrote:
> Hi Lib-Tech,
>
> I'm a freelance journalist covering the intersection of tech and politics.
> I'm wondering if any lib-techers know of or have experimented with ways to
> disable or reduce the sound from the long-rage acoustic devices that the
> NYPD has been deploying lately. LRADs were also used during Occupy.
>
> You know, maybe something like this? http://xkcd.com/368/ ;) (I know it
> doesn't quite work that way...)
>
> Protesters have been talking about the use of LRADs for a while now, but the
> Times just picked up on it in the recent #BlackLivesMatter/#ThisStopsToday
> protests:
>
> http://www.nytimes.com/2014/12/13/nyregion/lawyers-raise-concerns-over-shrill-device-used-by-police-during-garner-protests.html?
>
> If anyone knows of attempts to build such counter-measures or has ideas for
> how one might be built, please feel free to reply to me off-list.
>
> Thanks,
> Jay
>
> --
> Jay Cassano
> Freelance Journalist and Editor
> Senior Writer, Fast Company
> Technology Correspondent, Waging Nonviolence
> www.jcassano.net
> @jcassano
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  Scott Elcomb         @psema4
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