Federal and state eavesdropping statutes (sometimes called wiretapping or interception laws) typically prohibit the recording of private conversations absent consent from at least one person in that conversation.
Yet people in public places ¾for example, having a quiet conversation on a deserted street¾are often entitled to a reasonable expectation of privacy, without overhead microphones unexpectedly recording their conversation. Threats Posed by Acoustic Gunshot DetectionĮven if aimed at gunshots, this technology also captures human voices, at least some of the time. Other startups, such as Aegis, rely more heavily on artificial intelligence, and visual gun recognition, in recognizing potential shooting situations. It can be mounted on a vehicle and has been used in U.S. Raytheon produces the Boomerang system, which detects small arms fire. The company earned $34.75 million in revenue in 2018, and in March 2019, ShotSpotter announced it would be offering publicly traded stock. Currently, 100 cities are using ShotSpotter in the U.S., South Africa, and the Bahamas. ShotSpotter is by far the largest vendor of acoustic gunshot detection systems.
Mapping a potential gunshot on ShotSpotter's system. With microphones running and recording during the moments that it captures any sounds resembling gunshots, acoustic gunshot detection also records other sounds, including human voices, that occur within the vicinity of its microphones during a suspected shooting incident. It’s still up to people, sitting and listening on headphones, to say whether or not shots were fired. The sensors themselves can only determine whether there is a loud noise that somewhat resembles a gunshot. Location is determined by measuring the amount of time it takes for the sound to reach sensors in different locations.Īccording to ShotSpotter, the largest vendor of acoustic gunshot technology, this information is then verified by acoustic experts to confirm the sound is gunfire, and not a car backfire, fire crackers, or other sounds that could be mistaken for gun shots. If a gunshot is fired, the sensors detect the specific acoustic signature of a gunshot and send the exact time and location to the police.
The sound of a gunshot in words series#
Source: Īcoustic gunshot detection relies on a series of sensors, often placed on lamp posts or buildings. Minneapolis Shot Spotter Activation Call Locations in 2011. As is so often the case with police surveillance technologies, a device initially deployed for a less intrusive purpose (here, to report the sound and location of gunshots to police) is now being used for a far more intrusive purposes (to spy on people having conversations within the vicinity of their sensitive microphones). However, we now know that gunshot detection systems can also hear and record human voices¾and police have used these recordings as evidence in court. Police and companies that manufacture and sell acoustic gunshot detection systems have claimed that the point of this technology is to inform police of the location of shots fired, more quickly and accurately than relying on witnesses who overheard gun fire and who may call the police. They are usually mounted on street lights, or other elevated structures, though some mobile and fixed systems operate in both indoor and outdoor settings. The equipment usually takes the form of sensitive microphones and sensors, some of which must always be listening for the sound of gunshots. Acoustic gunshot detection is a system designed to detect, record, and locate the sound of gun fire and alert law enforcement.
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