Gunshot App Note

Detecting and Tracking Gunfire with Quantum's Vector Series QA-100

Detecting and Locating Gunshots

Gunshot Detection and Location with Quantum’s Vector Series Intrusion Detection Solution

A rapidly emerging challenge for critical infrastructure companies is providing adequate security against vandalism, crime, and sabotage, while minimizing the budgetary impact of such security. Recently, the possibility of sabotage by the malicious use of rifles or handguns fired at or into a facility has been added to the mix of potential threats.

The Quantum Technology Sciences security solution incorporates seismic-acoustic technology to create a perimeter security awareness zone around or bordering high value assets. The company added gunshot detection alerts to the array of potential threats that it can detect, classify, locate, and report to a user interface or to a larger or existing security management system.

A seismogram showing the amplitude of the ground vibrations from the gunshot report as a function of time. Gunshots produce a clear signal easily detected from  standoffs of 500m or more.

Quantum System Application for Gunshot Detection 

When a rifle or handgun is fired, in any direction, one omnipresent attribute of the gunshot is a sharp report at some decibel level due to the mass of rapidly expanding gases exiting the gun barrel. This generates an acoustic wave, or vibration, which propagates in all directions. Quantum’s seismic-acoustic sensor solution, detects and automatically processes these vibrations as they couple through the ground into a deployed sensor. Gunshot noise has singular vibrational attributes, and this enables the classification of a gunshot and the location of its origin to be reported.

When a handgun or rifle is fired within the detection range of a Quantum sensor, which for firearms exceeds 500 meters, the vibrations associated with the report excite the sensors and are detected, producing an electrical pattern known as a time series seismogram. These types of signals are known as “impulsive transients”. Within the sensor system, this energy is converted to an electrical signal which is further processed and analyzed by sophisticated software algorithms. For instance, initial signal processing transforms the seismogram pattern into a “spectrogram”, which displays the energy content of the source as functions of time and vibration frequency.

Quantum’s advanced software algorithms analyze the seismogram pattern, the spectrogram pattern, and other characteristics of the detected vibrations, all automatically and in real-time, to determine if the signal represents a gunshot detection. In this case, once classified as a gunshot with sufficient confidence, a gunshot detection alert is sent to the user interface.

A gunshot spectrogram, showing the energy distribution in the detected signal as a function of frequency and time. The greater the energy at a given frequency, the closer to the “red” end of the spectrum the colorization appears.

Quantum is also capable of using computational techniques to determine and report the location from where the shot was fired, all automatically and in real time. Whether the event to be located is a gunshot, a nuclear explosion, an underground facility, entrapped miners 1,000 feet underground, or an exploding or non-exploding artillery shell, one of Quantum’s strengths is in pinpointing the location of the source of seismic or acoustic vibrations.

Data processing is performed at or near the sensor locations, and only the resultant alerts are transmitted to the user or other output interface of the system. These minimal bytes of information can be acquired and graphically displayed on any user interface. Because the display requires only a short burst of information, integration of Quantum systems into existing security and surveillance systems to enhance their performance is very straightforward. Quantum systems can also stand alone or provide cues for cameras or UAVs or other customer system elements.

Summary Table for ammunition tested and characterized by Quantum to date

The Table lists the gun types and ammunition that have been tested at gunshot-to-sensor distances ranging up to 500 meters. Every weapon tested has been detectable and classifiable out to at least 500 meters. As can be seen, the weapons chosen represent a considerable breadth of firepower and accuracy range.

Spectrograms of a single .270 Winchester round fired from a prone position as sensed at three standoff distances.  There is some high frequency attenuation apparent at longer distances, and an increasing coda associated with the report with distance from the firing location.

Typical testing is done with sensors spaced from 100m to 500m away from the gunshot location. The figure above shows the seismograms of three shots fired from a rifle from a prone position using .270 caliber ammunition, as detected by sensors 100m, 300m, and 500m distant.  Note the high signal-to-noise ratios at all distances for all shots. The data is similar whether the firing is performed in the prone position (barrel 0.15 – 0.3 meters above the ground), a standing position (barrel 1.4 – 1.7 meters above the ground), or from a position on an elevated stand (barrel 2 – 3 meters above the ground).

The principal difference between 100m & 500m standoff gunshot detections is that the “ringing” or “echo” effect of the noise of the report becomes more extended at the greater distances. This portion of a transient impulse signal is known as its “coda”, and is illustrated clearly in the spectrograms shown here.

A gunshot detection report is seismically unique enough to minimize the likelihood of false positive classifications. For instance, the impulsive transient nature of a gunshot looks very much like the impulsive transient signal of footsteps, as shown in the below time series of footsteps preceding the firing of a .270 round from a rifle from a position on an elevated stand. However, when the time series seismogram is translated into a spectrographic representation, there are significant differences between the two, making it a straightforward task to computationally and statistically differentiate between these two sources of impulsive data and correctly classify as a gunshot detection.

 Comparison of footstep and gunshot signals.  These impulsive transient signals look similar in the time series, but the spectrogram reveals the gunshots to have a much larger spectral frequency range, simplifying the classification process and improving confidence in gunshot alerts.

The figure on the right shows a typical application to provide situation awareness around a electrical transmission substation to detect, classify, and report on footsteps and vehicles. The monitored area is more than 40 acres around the facility using only 8 sensors. With the software reconfigured for gunshot detection, classification, location, and reporting, the area coverage for potential weaponry threats expands to more than 340 acres.

Gunshot Detection Conclusion

Munitions fired into critical infrastructure facilities, such as substations, with malicious intent have the potential to cause property damage, to disrupt the transmission function of the facility, or even to initiate a cascading effect throughout the power grid, causing massive power losses that adversely affect public services and safety, and cause loss of productivity and expensive repairs/replacement. It is critical that any potential occurrences of gunshot detection be reported immediately as actionable information, specifically informing personnel that the threat is armed.

It is also highly desirable that a gunshot detection and reporting capability be integrated into existing or anticipated security system installations, to alleviate cost and complexity. The Quantum solution provides critical infrastructure, high value assets, oil & gas assets and borders with enhanced full area coverage for the potential threats presented by unauthorized footsteps, motor vehicles, digging, gunshots, and, upon request, several other activities identified as associated with potential threatening situations.

The  layout on the left is 8 sensors deployed to  monitor the area around a substation for the potential threats of footsteps and moving vehicles.  Arranged as shown, the 8 sensors monitor 43 acres of area. Equipping the sensors to monitor for gunshots as well produces the coverage pattern shown on the right, extending outward nearly 600m from the fence for the layout shown and monitoring 344 acres.