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Audio Engineers Built a Shield to Deflect Police Sound Cannons

158 points by elsewhen 6y ago

pjc50 6y ago
Amazing how in a supposedly litigious society like America it's possible to deploy a device which causes intentional, indiscriminate, permanent injury across a crowd and not get sued into oblivion. Bit like how tobacco, asbestos and Kinder eggs all incurred product liability because they weren't intending to be damaging to health, but gun manufacturers aren't liable because their products are supposed to be dangerous.
- rectang 6y ago
  I wonder if inflicting permanent disability without leaving any obvious physical traces on people that the police see as their adversaries is in fact part of what makes these devices attractive.
  - josefx 6y ago
    Similar to lethal injection, which looks more civilized than a bloody decapitation on the surface but can cause a slow and agonizing death to a completely paralyzed target?
  - DenisM 6y ago
    Are you saying that the police prefer dealing out permanent damage over non-permanent damage?
    - voxic11 6y ago
      No he is saying the police have no reason to prefer one to the other if the effects are hidden.
    - Novukus 6y ago
      Considering how rampant racism is in law enforcement (not even just in the US) as well as recent events in the US, I would actually say yes. It's "righteous punishment" for not submitting to the law (where law generally means whatever cops want you to do) and cops seem to enjoy that sort of thing.
- boomboomsubban 6y ago
  From the article, it seems more like these are only acceptable as the court cases are still pending.
  - hootbootscoot 6y ago
    They aren't prohibited for LE usage. They need to be. There should be a thorough review of all "less than lethal" crowd control tech. There are forces that seek to stop such reviews or even skirt oversight in principle, such as police unions...
    - TallGuyShort 6y ago
      >> less than lethal And for anyone not familiar with it, there was an excellent documentary on Netflix about the use of the Taser. It argued (and it argued well - I agree with it) that the Taser was attractive because it was less lethal than a gun, but it largely did not replace the gun, it replaced other submission methods. And it ended up being MORE lethal than those submission methods. And that's a problem if you misrepresent that. Now, I still think police should carry tasers because they're effective on a large spectrum of intermediate / gray area in the use of force continuum and it's much safer for police than many alternatives. But my point is that it's really bad to just think "less than lethal" is a cure-all. "Less lethal" can be lethal (or in this case, permanently disabling). There should still be a high threshold for deploying it.
      - deleted 6y ago
        [deleted]
      - Novukus 6y ago
        > Now, I still think police should carry tasers because they're effective on a large spectrum of intermediate / gray area in the use of force continuum and it's much safer for police than many alternatives. But my point is that it's really bad to just think "less than lethal" is a cure-all. "Less lethal" can be lethal (or in this case, permanently disabling). There should still be a high threshold for deploying it. I don't necessarily think that these kinds of non-lethal weapons can't be used in a "safe" or situationally appropriate way. The problem is that all of these non-lethal weapons have safety guidelines that need to be followed or else they're actually quite dangerous and have high rates of injury (even severe injury). As US law enforcement has shown repeatedly over recent weeks, they're not following any of these guidelines. People are being blinded because they're shooting rubber bullets at people's heads (against guidelines). They can't be trusted with these tools. I don't think it's solely a US problem either. French police is incredibly eager to liberally apply pepper spray to defenseless protesters (who've committed the heinous crime of exercising their right to free speech and their right to assemble). People are also injured whenever German police use water cannons.
- stainforth 6y ago
  Maybe because there is a continuously running thread in US society about who has impunity by default and who doesn't, expressed in the application of law and direction of capital.
- microcolonel 6y ago
  Law enforcement users are, in most places at least, not supposed to use them in the weapon mode on crowds, but rather as very annoying long range public address systems. When used as a weapon, of course, the same rules ought to apply as for any other police use of force. From the perspective of LRADs replacing other forms of PA, they should actually be an improvement in hearing safety, since the actual sound pressure should be lower for any given application.
- aquabeagle 6y ago
  And making a video about how to defend against them can get you sued. https://twitter.com/bennjordan/status/1268961057743294472 https://twitter.com/bennjordan/status/1268961057743294472 https://www.youtube.com/watch?v=3sqIvak-4Ek https://www.youtube.com/watch?v=3sqIvak-4Ek
- tw000001 6y ago
  Has anyone actually found any evidence of damage in the field? I did a cursory search but didn't find anything, though the wiki looks pretty corporatized (sanitized). OTOH people do like to claim damage from police more often than honesty would probably dictate...
- rexpop 6y ago
  > supposedly litigious society I am starting to think a certain, broad class of Americans is less litigious than, perhaps, the other.
  - pmiller2 6y ago
    I think you should spell it out rather than hinting. I have no idea what you're talking about.
    - Buttons840 6y ago
      The poor can't afford the litigation necessary for justice. The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France
      - pmiller2 6y ago
        Not just the poor. Very few individuals have the resources to assert their rights against corporations or government agencies via litigation.
        rexpop 6y ago
        I will happily adjust the definition of "poor" to those "lacking "the resources to assert their rights".
- aaron695 6y ago
  > permanent injury across a crowd This needs a real world citation. Wiki seems to me missing it too. "This article is missing information about non-loudspeaker / anti-personnel uses and hearing damage. (June 2019)" https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device Then, if there are any actual facts not political facts, we can talk about refusing police access to non-lethal weapons and only giving access to guns and what that might mean.
  - ashtonkem 6y ago
    The police already have guns, lots of them. The problem with less lethal crowd control tools is that police use them in situations where they would never use a real firearm, creating injuries that wouldn’t happen otherwise. This is really problematic when the police are angry at the protestors, as it gives them a way to inflict revenge pain without the PR fallout of opening fire with rifles. There is evidence that even on a regular basis, tasers have not replaced firearms, but instead have replaced other means of de-escalation and constraint. The result is that more americans might be dead because we’ve handed out tasers to cops without a second thought.
- sjg007 6y ago
  The Sandy Hook lawsuit might change things wrt guns.
kindatrue 6y ago
"The shield is also 50 lbs, so it’s not exactly easy to transport through a crowd." That's putting it mildly.
- boomboomsubban 6y ago
  Devices covering a larger area could be used in a kind of modern day barricade.
  - jascii 6y ago
    Or you could bring earplugs..
    - cp9 6y ago
      earplugs do literally nothing
      - jascii 6y ago
        From personal experience I can say that well-fitting earplugs did bring a significant reduction in pain-level. That is ofcourse a very limited and subjective observation, however: sound is sound, the laws of physics still hold.
      - deleted 6y ago
        [deleted]
    - boomboomsubban 6y ago
      The nice thing about barricades are that they protect large groups that may not have planned for the events.
      - jascii 6y ago
        But somebody needs to plan for those and arrange the logistics. Then, they end up being useless when LEO moves you elsewhere, and you probably lose them at the end of the day. I can stick a LOT of earplugs in my med-kit and hand them out when I see an LRAD..
bitwize 6y ago
Reflecting dangerous soundwaves back to the police may be prosecuted as assault on a police officer, a serious crime (automatic felony in NYC, for instance).
- ashtonkem 6y ago
  That really bugs me. If it’s a crime to reflect back onto the cops, why wasn’t it a crime for them to use it without justification?
  - gimboland 6y ago
    ~~without justification~~ FTFY.
    - ashtonkem 6y ago
      The past week has shown that cops are absolutely willing to use injurious force without even the slightest shred of justification, and then lie badly about it. In such a situation, it’s not clear why a group of people that acts this way should be given any equipment at all, let alone the legal authority to use it based on their own word alone.
      - yeetawayhn 6y ago
        > The past week has shown that cops are absolutely willing to use injurious force without even the slightest shred of justification, and then lie badly about it. But you just said you couldn't prove this above... Which is it?
        ashtonkem 6y ago
        You can’t prove a negative. You can however point out that no justification was given, or that the justification given was a blatant lie. Given that we live in a constitutional republic that provides rights to all citizens, any use of force on them that lacks justification is therefore unjustified.
imglorp 6y ago
Add some copper mesh or foil to the design, and you can block ADS as well! (microwave pain ray) https://en.wikipedia.org/wiki/Active_Denial_System https://en.wikipedia.org/wiki/Active_Denial_System
- non-entity 6y ago
  Dammit now I'm curious and have to research microwave pain rays
1024core 6y ago
> LRADs have been a part of anti-protest tactics since the mid 2000’s, when they were adopted by police after being used as a crowd control tool by U.S. military forces in Iraq and Afghanistan. Those who stand by idly while America does this to other people should remember that what we're inflicting on them will be inflicted on us tomorrow.
- drunkpotato 6y ago
  Or, you know, yesterday. And today. And also tomorrow. In the 1960's it was spraying civil rights marchers with firehoses. Now it's pepper balls and rubber bullets. "Less lethal" crowd control technology is too big a temptation for any authoritarian monster to resist.
- DenisM 6y ago
  >Those who stand by idly while America does this to other people should remember that what we're inflicting on them will be inflicted on us tomorrow. The US military used B2 bombers in Iraq. Do you expect these to be deployed in Seattle any time soon?
  - ceejayoz 6y ago
    > The US military used B2 bombers in Iraq. For crowd control?
  - Larrikin 6y ago
    Predator drones were deployed over the protests
  - minikites 6y ago
    >The US military used B2 bombers in Iraq. Do you expect these to be deployed in Seattle any time soon? https://en.wikipedia.org/wiki/MOVE#1985_bombing https://en.wikipedia.org/wiki/MOVE#1985_bombing >From a Pennsylvania State Police helicopter, Philadelphia Police Department Lt. Frank Powell proceeded to drop two one-pound bombs (which the police referred to as "entry devices") made of FBI-supplied Tovex, a dynamite substitute, targeting a fortified, bunker-like cubicle on the roof of the house. The resulting explosions ignited a fire from fuel for a gasoline-powered generator stored in the rooftop bunker. The fire spread and eventually destroyed approximately sixty-five nearby houses.
mrigor 6y ago
Do earplugs not work for these?
- sp332 6y ago
  Nope, your skull picks up the ultrasonic vibrations and delivers them to your eardrums. Kinda like bone-conduction headphones.
  - CountHackulus 6y ago
    The article claims that the LRADs in use do not use ultrasonics. However this is a good point for other directed-sound weapons that might be in use.
    - sp332 6y ago
      I was getting this confused with a different tech then. https://www.youtube.com/watch?v=HF9G9M0cR0E&t=170 https://www.youtube.com/watch?v=HF9G9M0cR0E&t=170
  - EForEndeavour 6y ago
    Ultrasonic? I thought the whole point of these devices is to produce ear-splitting tones that can actually be heard by humans. From the article: > According to a detailed teardown of the LRAD 300X posted by another audio technician, the LRADs produced by Genasys, the company that pioneered the devices, do not use an ultrasonic beam to project sound. However, Rife and Liberti say their design would still be effective against these hyper-directional blasts.
- barbegal 6y ago
  As long as the frequency is between 1 and 10kHZ then well fitting earplugs should reduce the pressure level by 20 to 30dB. If you combine with earmuffs or noise cancelling headphones then that could approach 40dB [1]. Indeed the manufacturer of one system recommends that operators use hearing protection such as earplugs [2]. [1] http://scienceandglobalsecurity.org/archive/sgs09altmann.pdf http://scienceandglobalsecurity.org/archive/sgs09altmann.pdf [2] http://www.adsx.co.za/information/faq-2/ http://www.adsx.co.za/information/faq-2/
ISL 6y ago
It seems like a corner-cube would do a serviceable job in this context and might be lighter, as long as the reflector is substantially larger than the wavelength of the sound. https://en.wikipedia.org/wiki/Corner_reflector https://en.wikipedia.org/wiki/Corner_reflector Wikipedia claims that the LRADs operate at ~2.5 kHz, which corresponds to ~13 cm wavelength. If a corner-cube is about the size of a protest sign, it might be sufficient? As a rule of thumb, if it is about as big as the LRAD device itself, it'll probably have some efficacy. The more-directional the LRAD is, the more effective the corner-cube will be. In Seattle, at least during "normal" protests, there are restrictions on the materials used in constructing protest signs (no wood bigger than 1", etc.) in order to limit the extent to which they can be used as weapons. One ought to be able to pretty-readily test whether or not foam-core-board corner-cubes (or any design) are effective reflectors with relatively low-intensity sound sources.
- shitpostbot 6y ago
  Protesters should make a parabolic reflector with the focus about 50ft out. Pretty sure cops would stop using these things instantly
  - ISL 6y ago
    Parabolic reflectors require alignment and they bring incident energy to a focus no matter what. Focusing the energy of an instrument that is designed to approach dangerous sound-intensity levels is certain to make the situation more dangerous. Non-violent action is predicated on the idea that hurting anyone, including an aggressor, is counterproductive. A corner-cube reflector won't hurt an LRAD operator any more than the LRAD operator is hurting others. A parabolic reflector could. If the golden rule isn't sufficient motivation to avoid a focal instrument, perhaps friendly-fire will be: A parabolic reflector will always bring parallel waves/rays to a focus at the focus. If the reflector is more than a focal-length inside a crowd, it is going to destroy the ears of a protestor. Like glass bottles that start fires in the Australian Outback by concentrating sunlight, anything that concentrates sound energy in an environment with an LRAD is a recipe for unintended consequence.
rozab 6y ago
>Rife and Liberti designed their shield to reflect audible sound waves that are condensed and carried via ultrasonic frequencies >According to a detailed teardown of the LRAD 300X posted by another audio technician, the LRADs produced by Genasys, the company that pioneered the devices, do not use an ultrasonic beam to project sound. It's an art piece. Someone figured out a way to get news coverage with minimal effort (and it really was very little effort). Check out their site: https://www.daveandgabe.care/ https://www.daveandgabe.care/
booleandilemma 6y ago
Can I get a couple of these for my apartment?
drummer 6y ago
In a similar way they will be able to use the beamforming capabilities of 5G for crowdcontrol once the stations are deployed everywhere.
- gruez 6y ago
  okay i'll bite. What's the power output for a "5G" station, and how much of that energy can be directed to a small area with beamforming? Finally, how does that figure compare to sunlight, which is around 1000W/m^2?
vzidex 6y ago
As someone who values their hearing - I religiously wear earplugs at concerts and muffs at the gun range - these absolutely terrify me. Good to see solutions, even if they're just initial prototypes that may/may not work, being developed.
deleted 6y ago
[deleted]

158 points by elsewhen 6y ago

Amazing how in a supposedly litigious society like America it's possible to deploy a device which causes intentional, indiscriminate, permanent injury across a crowd and not get sued into oblivion. Bit like how tobacco, asbestos and Kinder eggs all incurred product liability because they weren't intending to be damaging to health, but gun manufacturers aren't liable because their products are supposed to be dangerous.

rectang 6y ago
I wonder if inflicting permanent disability without leaving any obvious physical traces on people that the police see as their adversaries is in fact part of what makes these devices attractive.
- josefx 6y ago
  Similar to lethal injection, which looks more civilized than a bloody decapitation on the surface but can cause a slow and agonizing death to a completely paralyzed target?
- DenisM 6y ago
  Are you saying that the police prefer dealing out permanent damage over non-permanent damage?
  - voxic11 6y ago
    No he is saying the police have no reason to prefer one to the other if the effects are hidden.
  - Novukus 6y ago
    Considering how rampant racism is in law enforcement (not even just in the US) as well as recent events in the US, I would actually say yes. It's "righteous punishment" for not submitting to the law (where law generally means whatever cops want you to do) and cops seem to enjoy that sort of thing.
boomboomsubban 6y ago
From the article, it seems more like these are only acceptable as the court cases are still pending.
- hootbootscoot 6y ago
  They aren't prohibited for LE usage. They need to be. There should be a thorough review of all "less than lethal" crowd control tech. There are forces that seek to stop such reviews or even skirt oversight in principle, such as police unions...
  - TallGuyShort 6y ago
    >> less than lethal And for anyone not familiar with it, there was an excellent documentary on Netflix about the use of the Taser. It argued (and it argued well - I agree with it) that the Taser was attractive because it was less lethal than a gun, but it largely did not replace the gun, it replaced other submission methods. And it ended up being MORE lethal than those submission methods. And that's a problem if you misrepresent that. Now, I still think police should carry tasers because they're effective on a large spectrum of intermediate / gray area in the use of force continuum and it's much safer for police than many alternatives. But my point is that it's really bad to just think "less than lethal" is a cure-all. "Less lethal" can be lethal (or in this case, permanently disabling). There should still be a high threshold for deploying it.
    - deleted 6y ago
      [deleted]
    - Novukus 6y ago
      > Now, I still think police should carry tasers because they're effective on a large spectrum of intermediate / gray area in the use of force continuum and it's much safer for police than many alternatives. But my point is that it's really bad to just think "less than lethal" is a cure-all. "Less lethal" can be lethal (or in this case, permanently disabling). There should still be a high threshold for deploying it. I don't necessarily think that these kinds of non-lethal weapons can't be used in a "safe" or situationally appropriate way. The problem is that all of these non-lethal weapons have safety guidelines that need to be followed or else they're actually quite dangerous and have high rates of injury (even severe injury). As US law enforcement has shown repeatedly over recent weeks, they're not following any of these guidelines. People are being blinded because they're shooting rubber bullets at people's heads (against guidelines). They can't be trusted with these tools. I don't think it's solely a US problem either. French police is incredibly eager to liberally apply pepper spray to defenseless protesters (who've committed the heinous crime of exercising their right to free speech and their right to assemble). People are also injured whenever German police use water cannons.
stainforth 6y ago
Maybe because there is a continuously running thread in US society about who has impunity by default and who doesn't, expressed in the application of law and direction of capital.
microcolonel 6y ago
Law enforcement users are, in most places at least, not supposed to use them in the weapon mode on crowds, but rather as very annoying long range public address systems. When used as a weapon, of course, the same rules ought to apply as for any other police use of force. From the perspective of LRADs replacing other forms of PA, they should actually be an improvement in hearing safety, since the actual sound pressure should be lower for any given application.
aquabeagle 6y ago
And making a video about how to defend against them can get you sued. https://twitter.com/bennjordan/status/1268961057743294472 https://twitter.com/bennjordan/status/1268961057743294472 https://www.youtube.com/watch?v=3sqIvak-4Ek https://www.youtube.com/watch?v=3sqIvak-4Ek
tw000001 6y ago
Has anyone actually found any evidence of damage in the field? I did a cursory search but didn't find anything, though the wiki looks pretty corporatized (sanitized). OTOH people do like to claim damage from police more often than honesty would probably dictate...
rexpop 6y ago
> supposedly litigious society I am starting to think a certain, broad class of Americans is less litigious than, perhaps, the other.
- pmiller2 6y ago
  I think you should spell it out rather than hinting. I have no idea what you're talking about.
  - Buttons840 6y ago
    The poor can't afford the litigation necessary for justice. The law, in its majestic equality, forbids the rich as well as the poor to sleep under bridges, to beg in the streets, and to steal bread. - Anatole France
    - pmiller2 6y ago
      Not just the poor. Very few individuals have the resources to assert their rights against corporations or government agencies via litigation.
      - rexpop 6y ago
        I will happily adjust the definition of "poor" to those "lacking "the resources to assert their rights".
aaron695 6y ago
> permanent injury across a crowd This needs a real world citation. Wiki seems to me missing it too. "This article is missing information about non-loudspeaker / anti-personnel uses and hearing damage. (June 2019)" https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device https://en.wikipedia.org/wiki/Long_Range_Acoustic_Device Then, if there are any actual facts not political facts, we can talk about refusing police access to non-lethal weapons and only giving access to guns and what that might mean.
- ashtonkem 6y ago
  The police already have guns, lots of them. The problem with less lethal crowd control tools is that police use them in situations where they would never use a real firearm, creating injuries that wouldn’t happen otherwise. This is really problematic when the police are angry at the protestors, as it gives them a way to inflict revenge pain without the PR fallout of opening fire with rifles. There is evidence that even on a regular basis, tasers have not replaced firearms, but instead have replaced other means of de-escalation and constraint. The result is that more americans might be dead because we’ve handed out tasers to cops without a second thought.
sjg007 6y ago
The Sandy Hook lawsuit might change things wrt guns.

kindatrue 6y ago

"The shield is also 50 lbs, so it’s not exactly easy to transport through a crowd." That's putting it mildly.

boomboomsubban 6y ago
Devices covering a larger area could be used in a kind of modern day barricade.
- jascii 6y ago
  Or you could bring earplugs..
  - cp9 6y ago
    earplugs do literally nothing
    - jascii 6y ago
      From personal experience I can say that well-fitting earplugs did bring a significant reduction in pain-level. That is ofcourse a very limited and subjective observation, however: sound is sound, the laws of physics still hold.
    - deleted 6y ago
      [deleted]
  - boomboomsubban 6y ago
    The nice thing about barricades are that they protect large groups that may not have planned for the events.
    - jascii 6y ago
      But somebody needs to plan for those and arrange the logistics. Then, they end up being useless when LEO moves you elsewhere, and you probably lose them at the end of the day. I can stick a LOT of earplugs in my med-kit and hand them out when I see an LRAD..

bitwize 6y ago

Reflecting dangerous soundwaves back to the police may be prosecuted as assault on a police officer, a serious crime (automatic felony in NYC, for instance).

ashtonkem 6y ago
That really bugs me. If it’s a crime to reflect back onto the cops, why wasn’t it a crime for them to use it without justification?
- gimboland 6y ago
  ~~without justification~~ FTFY.
  - ashtonkem 6y ago
    The past week has shown that cops are absolutely willing to use injurious force without even the slightest shred of justification, and then lie badly about it. In such a situation, it’s not clear why a group of people that acts this way should be given any equipment at all, let alone the legal authority to use it based on their own word alone.
    - yeetawayhn 6y ago
      > The past week has shown that cops are absolutely willing to use injurious force without even the slightest shred of justification, and then lie badly about it. But you just said you couldn't prove this above... Which is it?
      - ashtonkem 6y ago
        You can’t prove a negative. You can however point out that no justification was given, or that the justification given was a blatant lie. Given that we live in a constitutional republic that provides rights to all citizens, any use of force on them that lacks justification is therefore unjustified.

imglorp 6y ago

Add some copper mesh or foil to the design, and you can block ADS as well! (microwave pain ray) https://en.wikipedia.org/wiki/Active_Denial_System https://en.wikipedia.org/wiki/Active_Denial_System

non-entity 6y ago
Dammit now I'm curious and have to research microwave pain rays

1024core 6y ago

> LRADs have been a part of anti-protest tactics since the mid 2000’s, when they were adopted by police after being used as a crowd control tool by U.S. military forces in Iraq and Afghanistan. Those who stand by idly while America does this to other people should remember that what we're inflicting on them will be inflicted on us tomorrow.

drunkpotato 6y ago
Or, you know, yesterday. And today. And also tomorrow. In the 1960's it was spraying civil rights marchers with firehoses. Now it's pepper balls and rubber bullets. "Less lethal" crowd control technology is too big a temptation for any authoritarian monster to resist.
DenisM 6y ago
>Those who stand by idly while America does this to other people should remember that what we're inflicting on them will be inflicted on us tomorrow. The US military used B2 bombers in Iraq. Do you expect these to be deployed in Seattle any time soon?
- ceejayoz 6y ago
  > The US military used B2 bombers in Iraq. For crowd control?
- Larrikin 6y ago
  Predator drones were deployed over the protests
- minikites 6y ago
  >The US military used B2 bombers in Iraq. Do you expect these to be deployed in Seattle any time soon? https://en.wikipedia.org/wiki/MOVE#1985_bombing https://en.wikipedia.org/wiki/MOVE#1985_bombing >From a Pennsylvania State Police helicopter, Philadelphia Police Department Lt. Frank Powell proceeded to drop two one-pound bombs (which the police referred to as "entry devices") made of FBI-supplied Tovex, a dynamite substitute, targeting a fortified, bunker-like cubicle on the roof of the house. The resulting explosions ignited a fire from fuel for a gasoline-powered generator stored in the rooftop bunker. The fire spread and eventually destroyed approximately sixty-five nearby houses.

mrigor 6y ago

Do earplugs not work for these?

sp332 6y ago
Nope, your skull picks up the ultrasonic vibrations and delivers them to your eardrums. Kinda like bone-conduction headphones.
- CountHackulus 6y ago
  The article claims that the LRADs in use do not use ultrasonics. However this is a good point for other directed-sound weapons that might be in use.
  - sp332 6y ago
    I was getting this confused with a different tech then. https://www.youtube.com/watch?v=HF9G9M0cR0E&t=170 https://www.youtube.com/watch?v=HF9G9M0cR0E&t=170
- EForEndeavour 6y ago
  Ultrasonic? I thought the whole point of these devices is to produce ear-splitting tones that can actually be heard by humans. From the article: > According to a detailed teardown of the LRAD 300X posted by another audio technician, the LRADs produced by Genasys, the company that pioneered the devices, do not use an ultrasonic beam to project sound. However, Rife and Liberti say their design would still be effective against these hyper-directional blasts.
barbegal 6y ago
As long as the frequency is between 1 and 10kHZ then well fitting earplugs should reduce the pressure level by 20 to 30dB. If you combine with earmuffs or noise cancelling headphones then that could approach 40dB [1]. Indeed the manufacturer of one system recommends that operators use hearing protection such as earplugs [2]. [1] http://scienceandglobalsecurity.org/archive/sgs09altmann.pdf http://scienceandglobalsecurity.org/archive/sgs09altmann.pdf [2] http://www.adsx.co.za/information/faq-2/ http://www.adsx.co.za/information/faq-2/

ISL 6y ago

It seems like a corner-cube would do a serviceable job in this context and might be lighter, as long as the reflector is substantially larger than the wavelength of the sound. https://en.wikipedia.org/wiki/Corner_reflector https://en.wikipedia.org/wiki/Corner_reflector Wikipedia claims that the LRADs operate at ~2.5 kHz, which corresponds to ~13 cm wavelength. If a corner-cube is about the size of a protest sign, it might be sufficient? As a rule of thumb, if it is about as big as the LRAD device itself, it'll probably have some efficacy. The more-directional the LRAD is, the more effective the corner-cube will be. In Seattle, at least during "normal" protests, there are restrictions on the materials used in constructing protest signs (no wood bigger than 1", etc.) in order to limit the extent to which they can be used as weapons. One ought to be able to pretty-readily test whether or not foam-core-board corner-cubes (or any design) are effective reflectors with relatively low-intensity sound sources.

shitpostbot 6y ago
Protesters should make a parabolic reflector with the focus about 50ft out. Pretty sure cops would stop using these things instantly
- ISL 6y ago
  Parabolic reflectors require alignment and they bring incident energy to a focus no matter what. Focusing the energy of an instrument that is designed to approach dangerous sound-intensity levels is certain to make the situation more dangerous. Non-violent action is predicated on the idea that hurting anyone, including an aggressor, is counterproductive. A corner-cube reflector won't hurt an LRAD operator any more than the LRAD operator is hurting others. A parabolic reflector could. If the golden rule isn't sufficient motivation to avoid a focal instrument, perhaps friendly-fire will be: A parabolic reflector will always bring parallel waves/rays to a focus at the focus. If the reflector is more than a focal-length inside a crowd, it is going to destroy the ears of a protestor. Like glass bottles that start fires in the Australian Outback by concentrating sunlight, anything that concentrates sound energy in an environment with an LRAD is a recipe for unintended consequence.

rozab 6y ago

>Rife and Liberti designed their shield to reflect audible sound waves that are condensed and carried via ultrasonic frequencies >According to a detailed teardown of the LRAD 300X posted by another audio technician, the LRADs produced by Genasys, the company that pioneered the devices, do not use an ultrasonic beam to project sound. It's an art piece. Someone figured out a way to get news coverage with minimal effort (and it really was very little effort). Check out their site: https://www.daveandgabe.care/ https://www.daveandgabe.care/

booleandilemma 6y ago

Can I get a couple of these for my apartment?

drummer 6y ago

In a similar way they will be able to use the beamforming capabilities of 5G for crowdcontrol once the stations are deployed everywhere.

gruez 6y ago
okay i'll bite. What's the power output for a "5G" station, and how much of that energy can be directed to a small area with beamforming? Finally, how does that figure compare to sunlight, which is around 1000W/m^2?

vzidex 6y ago

As someone who values their hearing - I religiously wear earplugs at concerts and muffs at the gun range - these absolutely terrify me. Good to see solutions, even if they're just initial prototypes that may/may not work, being developed.

deleted 6y ago

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