Question: In the security industry, where can some of the best examples of the intersection of the analog and digital worlds be found? Answer: in special sound detection devices (SSDD). Because sound, by its very nature, is an analog function, the security industry has done an excellent job in adapting robust digital detection technologies to detect and alert.
This sound detection is normally accomplished by identifying a unique sound algorithm or pattern. The suspect sound waves are broken into minute digital slices using a technology called analog to digital conversion (ADC). Once this sound is in digital form, powerful and economical application specific integrated circuits (ASIC) along with digital signal processor (DSP) programming allows the alarm sound detection device to identify the particular sound it was designed to catch.
I’ve noticed some new and interesting SSDD applications on the market. So let’s take a look at the many ways security professionals can provide unique sound detection products and services.
Acoustical Glass Break Detection (AGBD) — This is probably one of the most popular SSDD applications, which you’ve heard me talk about in great detail in past columns. However, it never hurts to review some important AGBD installation and testing tips. These devices typically listen for a combination of low frequency or infrasonic sounds from the flexing of the glass, and higher, crisp sounds from the actual breaking of the glass. Listening only for these unique sound pairings helps prevent these devices from being falsely tripped by other similar environmental sounds.
The best overall AGBD tip is that technicians should always carefully follow the manufacturer’s installation and testing instructions. It is typically best to place these detectors facing the protected glass and not rely on the reflective nature of sound. Make sure to use the correct device settings for the type of glass (e.g. laminated, reinforced and plate). Only use the manufacturer’s approved tester and don’t just throw your keys at the wall. Always test with all the room furnishings in place as they will considerably reduce sound detection performance — remember, sound waves are very directional and can easily be blocked or attenuated. If you are testing glass behind drapes, make sure the tester is triggered from behind the drapes as well. As with all security devices, failure to properly install and test can be deadly. UL 639 and UL 681 are relevant standards.
Drone Detection — The big buzz these days is drones. As we’ve seen in the news, they are coming to a neighborhood near you. Well it seems that these RC helicopter type drones, quadrotors, etc., emit unique sound patterns that — yes, you guessed it — can be detected. One example is a newly formed company called DroneShield. According to the manufacturer the device will listen for drones (see photo), scan its database for common drone acoustic signatures and ignore other common sounds such as lawn mowers and leaf blowers. Some interesting applications include detecting: paparazzi cameras for your high-profile customers, drones dropping guns into prison courtyards, illegal aerial video recordings in various public and private venues, and trespassing alerts for drones straying in airport space.
Gunshot Detection — The sound of gunfire has a unique signature. We’ve all heard news reports about shootings in public places like schools, universities and malls; solutions such as the Red Alertt Gunshot Alarm System can assist in the rapid detection and location of gunfire and report this information to security and local law enforcement. These fully automated systems are also being used to quickly locate gunfire across an entire city or county.
Graffiti Detection — Did you know that the United States spends more than $25 billion annually on graffiti abatement? Elmdene, a division of Potter, long known for sound detection technologies, has a new system called the Merlin Graffiti Detector. When placed high on exterior walls, this specialized listening device is able to detect aerosol can activity up to 25 feet in a 120° detection zone. It can interface standard alarm panels with its relay contacts. Police relish the opportunity with a silent alarm to catch graffiti “taggers” in the act.
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