Long range acoustic device
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The LRAD is the round black device on top of the New York City police
Hummer.

The long range acoustic device (LRAD) is a crowd-control and hailing
device developed by American Technology Corporation.

According to the manufacturer's specifications, the equipment weighs
45 pounds (20 kg) and can emit sound in a 30° beam (only at high
frequency, 2.5 kHz) from a device 33 inches (83 cm) in diameter. At
maximum volume, it can emit a warning tone that is 146 dBSPL (1,000
W/m²) at 1 metre, a level that is capable of permanently damaging
hearing, and higher than the normal human threshold of pain (120 – 140
dB). The maximum usable design range extends to 300 metres. At 300
metres, the warning tone (measured) is less than 90 dB. The warning
tone is a high-pitched shrill tone similar to that of a smoke detector.

There appears to be some disagreement over these specifications, as
some have reported measurements that differ from the manufacturer's
specifications, and show reduced output with a less directive beam.

It's instructive to note that any loudspeaker of equal size will
generate a beam of the same directivity as LRAD. The parameter "ka",
which is the wave number multiplied by the speaker radius, is often
used to characterize sound source directivity. For this source, ka=19
at 2.5kHz, and according to the LRAD data sheet, the beam angle of
about 30 degrees total - precisely what is predicted for a regular
loudspeaker [1]. Contrary to some beliefs, the device does not use
ultrasound, nor is it a phased array; it uses an array of conventional
acoustic tweeters, the same as those used in many professional audio
applications, all driven together in parallel.[citation needed]

Carl Gruenler, (former) vice president of military and government
operations for American Technology Corp. (and who now runs a company
making a competing device), says that being within 100 yards (90 m) of
the device is extremely painful, but its use should be limited to 300
yards (270 m) to be effectively used. He concedes that the device is
powerful enough to cause permanent auditory damage, but that it is
only meant to be used for a few seconds at a time.

Countermeasures may include the use of passive hearing protection
(earplugs, headsets), which may bring the sound down to ineffective
levels. In addition, sound could be reflected from a solid surface,
and redirected back to the originator.

Small spherical "point-source" acoustic devices follow the known
inverse square law, which predicts the loss of 6db per doubling of
distance from the source. Large speakers (or large arrays), such as
these mentioned above or those commonly used in concert halls, etc.,
produce less loss with distance in the nearfield, typically 3-4db per
doubling of distance from the source. The larger the speaker, and the
higher the frequency, the longer the effective nearfield is (see
Beranek). Devices like this generally have nearfields of only a few
meters.

[edit] Usage
The LRAD in use on a U.S. Navy patrol ship.
LRAD on RMS Queen Mary 2

The device was originally intended to be used by American warships to
warn incoming vessels approaching without permission, and some reports
claim that this is now a "non-lethal weapon". Its output up to 155db,
focused at a distance, is sufficient to produce permanent ear damage
and temporarily disrupt vision.[2] It may also be used simply as a
very effective megaphone prior to any use as a weapon.

These devices are currently used at Camp Bucca Iraq and are being
tested in regions of Baghdad, Fallujah, along with other regions of
Iraq. The LRAD device was also used by police in New York City during
protests of the 2004 Republican National Convention[3] and in Georgia
against opposition protesters in Tbilisi on November 2007 [4][5].

The luxury cruise ship Seabourn Spirit employed an LRAD while
repelling pirates who attacked the vessel with RPGs about 160 km off
the coast of Somalia in early November 2005.[6] [7] The effectiveness
of this device during the attack is not completely clear, but the
pirates did not succeed in boarding the vessel and eventually fled.

The Liberian vessel MV Biscaglia was attacked on November 28, 2008.
The security detachment aboard Biscaglia used an LRAD device in an
effort to repel attackers armed with assault rifles and
rocket-propelled grenades. Following a one-sided shootout, the ship
was seized and the unarmed security contractors forced to abandon ship
or be killed.[8] The incident caused the usefulness of LRADs to be
called into question by Lloyd's List.[9]


--- In brutalsfx@yahoogroups.com, "Pengochi The Badoon"
<beakfastars@...> wrote:
>
> who are the terrorists.the police?
>
>
> --- In brutalsfx@yahoogroups.com, frankenfag <no_reply@> wrote:
> >
> > The New York Police Department wants to be able to shut down cell
> > phones, in case of a terrorist attack. In testimony today before the
> > Senate Committee on Homeland Security and Governmental Affairs, New
> > York Police Commissioner Ray Kelly said he wanted to take out that
> > "formidable capacity to adjust tactics while attacks are underway."
> > http://blog.wired.com/defense/2009/01/nypd-eyes-disru.html
> >
> > Digg if you feel so inclined
> >
>
http://digg.com/gadgets/NYPD_Wants_to_Jam_Cell_Phones_During_Terror_Attack
> >
>