AHD – Acoustic Hailing Device

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What is an Acoustic Hailing Device or AHD?
The Acoustic Hailing Device or AHD is a loudspeaker system specifically designed to be very loud and highly directive. As the name implies, they are loudspeaker systems engineered for one purpose; to deliver a startlingly loud and clear, audible message over large distances or to large groups of people. For these reasons, Acoustic Hailing Devices have become invaluable tools for law enforcement, fire departments, search and rescue, and anywhere it’s advantageous to give verbal instructions at a distance.

AHDs come in a wide variety of system types, from small and portable to fixed remotely operated devices capable of delivering high decibel signals more than a mile. Most Acoustic Hailing Devices are made using traditional loudspeaker technology, but they’re designed to be highly directive and limited in bandwidth, optimized for speech and higher frequency tones. Most systems include the ability to play pre-recorded messages and preannounce or warning tones.


To deliver sound at longer distances and higher levels than traditional loudspeakers, AHDs utilize arrays of ultrasonic transducers following a principle called theoretical ultrasonic nonlinear acoustics. AHDs encode audible sounds by modulating them with ultrasonic carrier waves. These systems can produce such high energy over long distances that it’s possible to inflict pain or physical harm to people in their field of directivity.

AHDs are valuable for making public address announcements to large or noisy crowds; however, the decibel level can be set high enough to be unsafe, causing temporary or permanent hearing loss. For this reason, AHDs are sometimes referred to as acoustic weapons.

What’s the Difference between an AHD, LRAD and LRAW?
AHDs come in a wide variety of configurations – large and small for use at short range and very long distances. The distinction between AHD (Acoustic Hailing Device), LRAD (Long Range Acoustic Device), and LRAW (Long Range Acoustic Weapon) is not defined by the technology but by the system’s intended use. So, the terms AHD, LRAD and LRAW can all be used interchangeably. An LRAD is a powerful and versatile instrument of communication. LRADs can be valuable when used at large demonstrations, active shooter events, tactical standoffs, evacuations, and natural disasters.

LRADs as a Sonic Weapon
LRADS are ideal for non-lethal, non-kinetic crowd control. For this reason, AHDs are sometimes referred to as acoustic weapons. LRADs are widely used by law enforcement agencies to serve warrants, in standoffs to  communicate with suspects, riots, and other situations that can be de-escalated by communicating from a distance.

Torrence is an authorized distributor of AHD devices. We have the expertise to design and safely configure these tools for use in Mass Notification, Evacuation, and Law Enforcement. Contact us for more information and to discuss your application.

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