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 <[email protected]> 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 > -- > Liberationtech is public & archives are searchable on Google. Violations of > list guidelines will get you moderated: > https://mailman.stanford.edu/mailman/listinfo/liberationtech. Unsubscribe, > change to digest, or change password by emailing moderator at > [email protected]. -- Scott Elcomb @psema4 http://psema4.com/pubkey.txt http://www.pirateparty.ca/ -- Liberationtech is public & archives are searchable on Google. Violations of list guidelines will get you moderated: https://mailman.stanford.edu/mailman/listinfo/liberationtech. Unsubscribe, change to digest, or change password by emailing moderator at [email protected].
