Sound Devices at Demonstrations: How LRAD Systems Work
During protests in the USA, security authorities use LRAD systems for announcements and crowd control. How do these "sound cannons" work?
(Image: Marie Kanger Born / Shutterstock.com / Bearbeitung heise medien)
Last week, during protests against operations by the US Immigration and Customs Enforcement (ICE) in Minnesota, vehicles with rectangular structures were spotted – some were military Humvees, others civilian vehicles. These structures are typical for Long-Range Acoustic Devices (LRAD). CBS News reported on January 27th about the use of an LRAD for announcements by the Minnesota State Patrol in Maple Grove.
Videos of the demonstrations show people recoiling even from a test announcement made by such a device. Military experts and former operatives describe the effect of LRAD announcements as unusually intense, “like hearing the voice of God in your head.”
How LRAD Works
But how does this drastic effect come about? Unlike conventional loudspeakers and megaphones, which scatter sound broadly, LRAD systems generate a highly directional beam of sound, which is why they are sometimes referred to as “sound cannons.”
Technically, they are usually constructed as a flat transducer array: many individual sound transducers work together and are supported by driver/waveguide technology to emit as much sound energy forward as possible. The beamforming is achieved through superposition (interference): in the target cone, the sound waves from many transducers add up, while lateral radiation is significantly reduced (depending on geometry and control) and sometimes canceled out. This array-based beamforming (comparable to principles of phased array technology) creates a narrow beam with very high volume. This allows speech and warning tones to be bundled and transmitted comprehensibly over long distances.
Maximum ranges, depending on the model, are between 600 and 5,500 meters under ideal conditions. In practice, range and speech intelligibility depend on factors such as ambient noise, wind, and orientation. Some data sheets differentiate between “maximum range” and a lower “operational range” in high background noise.
The sound beam can be directed like an acoustic spotlight onto individuals or groups. Outside the main beam, the sound coverage is reduced, but reflections can cause very loud noise in the surrounding area.
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Development and Manufacturer
The technology was developed in the early 2000s by American Technology Corporation (now Genasys Inc.) in response to the bombing of the USS Cole, which showed that better tools for communication and warning at a distance were needed. The devices used in Minnesota are likely to be LRAD systems from the manufacturer Genasys.
The manufacturer officially positions the devices as communication and warning systems with the aim of “clear communication, safety, and control – anytime, anywhere.” The systems also have a “Deterrent” function, which, according to the manufacturer, is intended to cause discomfort without causing permanent damage.
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Communication and Deterrence – Two Sides of a Technology
LRAD systems can be operated in two fundamentally different modes: as a communication system and as an acoustic deterrent.
In communication mode, live announcements and audio recordings can be broadcast over several kilometers. Instructions remain understandable even in chaotic situations.
In deterrence mode, LRAD can emit a high, shrill alarm or other deterrent tones. Depending on the model, data sheets cite peak levels of up to 160 dB SPL (sound pressure level) at 1 meter distance, while continuous levels are lower. The devices are optimized for the particularly sensitive hearing range of humans between approximately 1 and 5 kHz, which improves speech intelligibility at moderate levels and increases discomfort at high levels.
This dual functionality leads to different application scenarios: in shipping, the systems are used for communication and piracy prevention. In disaster management, they enable warnings over long distances. In industry, they are used for bird control.
However, the systems are increasingly being used for crowd control. In the USA, LRAD devices have been in use by police units for years. Genasys stated in 2024 that LRADs “now play a crucial role in managing civil unrest” and are needed by law enforcement agencies “in the face of numerous challenges, including elections, political conventions, and actions by organized protest groups.”
Police and security forces use the systems at demonstrations and in crowd management. The systems enable acoustic pressure without physical force. In some cases, the mere visible presence of an LRAD device is enough to influence people.
In border protection, LRAD systems have long been used in the USA along the southern border. Approaching individuals are threatened with immediate arrest via announcement if they cross the border.
The military uses the systems not only for communication with its forces but also for psychological influence in conflict zones. Since no speaker is visible, the loud announcements appear to come from an indeterminate direction – an effect used to create confusion and uncertainty.
Health Risks and Controversial Deployments
In the direct beam, these tones in the kHz range can cause severe pain, disorientation, and nausea. Unprotected ears are at significant risk of acute and permanent hearing damage. The manual for the “LRAD 500X” system warns operators about the possibility of hearing loss when using the device.
Human rights and health organizations critically assess the use of these devices at demonstrations. Organizations such as Amnesty International, the American Civil Liberties Union (ACLU), and Physicians for Human Rights see a potential misuse as an acoustic weapon system, especially at short distances and without prior warning.
The controversy surrounding LRAD deployments is not limited to the USA. An internationally documented case occurred on March 17, 2025, in Belgrade, Serbia. Investigations by the organization Earshot suggest that an LRAD system was used there. The Serbian government confirmed the presence of a vehicle with an LRAD system at the scene but denied its use.
(olb)
