Time is of the essence. When an active shooting occurs, the key to preventing and/or minimizing injuries and death is quickly identifying exactly where the shooter is, end the threat and then treat and transport victims.

Gunshots have unique audio characteristics so microphones can detect and provide information for location analysis. With its ShotSpotter site security system, SST, Inc., the leader in gunshot detection and location technology, offers systems for both indoor and outdoor gunshot detection. For indoors, it is the Gunfire Detection and Alert System (GDAS) and for outdoors, it is Wide Area Acoustic Surveillance (WAAS). The key to each is multiple sensing locations.

In an outdoor system, an air-acoustic detection grid has several distributed sensor modules with a GPS receiver for determining the position of the acoustic sensor. Each sensor is an omnidirectional microphone with a bandwidth of 50-14,000 Hz for sensing acoustic energy.

When a sensor detects a pulse, the waveform of the pulse has information including sharpness, strength, duration and decay time. Using sensor-based analysis, integrated software analyzes the audio signals and if at least three sensors detect a pulse suspected to be a gunshot, the sensors then send a small data packet to cloud servers. Using multilateration, or hyperbolic positioning, the time difference of arrival and angle of arrival of the sound from each determines a precise location.

Once the system classifies an occurrence as likely gunfire, it transmits details to acoustic experts in an Incident Review Center (IRC) for additional analysis. If confirmed, the system publishes the alert notification to law enforcement and emergency responders. From initial gunfire detection to alert, the entire process takes less than 60 seconds.