Search Mailing List Archives

Limit search to: Subject & Body Subject Author
Sort by: Reverse Sort
Limit to: All This Week Last Week This Month Last Month
Select Date Range     through    

[liberationtech] LRAD counter-measures?

Scott Elcomb psema4 at
Mon Dec 15 17:03:43 PST 2014

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)

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:

On Sun, Dec 14, 2014 at 6:05 PM, Jay Cassano <jay at> 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? ;) (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:
> 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
> @jcassano
> --
> Liberationtech is public & archives are searchable on Google. Violations of
> list guidelines will get you moderated:
> Unsubscribe,
> change to digest, or change password by emailing moderator at
> companys at

  Scott Elcomb         @psema4

More information about the liberationtech mailing list