Minimizing Gunshot Detection False Positives

Abstract

This invention is a gunshot detection device that provides very reliable inside and outside real-time situational awareness of gunshot events, while reducing Gunshot Detection False Positives and Negatives.

Claims

1. (canceled)

2. (canceled)

3. A system for detecting a gunshot comprising: a device for capturing acoustic data that is potentially sound emanating from an actual gunshot; circuitry configured to receive electrical signals and to generate digital signals comprising digital data which corresponds to the received acoustic data; a processor including non-transitory, computer-readable medium comprising computer-executable instructions for determining whether the captured acoustic data or sampled portions of the captured acoustic data contains an ultrasonic burst that corresponds to an ultrasonic signature of an actual gunshot having contiguous ultrasonic component sound frequency content in excess of 20 kHz, whereby the determination is used to identify an actual gunshot and distinguish it from that of a sound burst that is not an actual gunshot.

4. The system of claim 3, wherein the device captures the acoustic data at a sampling rate that is at least twice the highest discrete ultrasonic frequency sought to be captured.

5. The system of claim 3, wherein the circuitry generates the digital signals by calculating a Fast Fourier Transformation (FFT) in accordance with any known FFT algorithm.

6. The system of claim 3, wherein the circuitry generates the digital signals by calculating a Fast Fourier Transformation (FFT) in accordance with known FFT implementation.

7. The system of claim 3, wherein the circuitry generates the digital signals by creating a spectrogram having a spectrum of frequencies of the signal as it varies with time, and further detects an impulse prior to generating the digital signals that yields the spectrogram.

8. The system of claim 3, wherein the computer-executable instructions further cause the system to transmit the captured acoustic data to a second location for storage or further processing.

9. The system of claim 3, wherein the circuitry generates the digital signals by creating a spectrogram having a spectrum of frequencies of the signal as it varies with time, and the computer-executable instructions further cause the system to transmit the spectrogram to a second location for storage or further processing

10. The system of claim 3, wherein the circuitry generates the digital signals by creating a spectrum of frequencies over a short period of time, and the computer-executable instructions further cause the system to transmit the spectrum to a second location for storage or further processing.

11. The system of claim 3, wherein the computer-executable instructions further cause the system to transmit the captured acoustic data to a second location prior to the circuitry generating the digital signals that yields the spectrogram.

12. The system of claim 3, wherein, responsive to a gunshot determination, the computer-executable instructions further cause the system to record at least one of a date and time of occurrence of the determination.

13. A method for detecting a gunshot, comprising: providing a device for capturing acoustic data that is potentially sound emanating from an actual gunshot; providing circuitry configured to receive electrical signals and to generate digital signals comprising digital data which corresponds to the received acoustic data; determining whether the captured acoustic data or sampled portions of the captured acoustic data contains an ultrasonic burst that corresponds to an ultrasonic signature of an actual gunshot having contiguous ultrasonic component sound frequency content in excess of 20 kHz, whereby the determination is used to identify an actual gunshot and distinguish it from that of a sound burst that is not an actual gunshot.

14. The method of claim 13, wherein the device captures the acoustic data at a sampling rate that is at least twice the highest discrete ultrasonic frequency sought to be captured.

15. The method of claim 13, wherein the circuitry generates the digital signals by calculating a Fast Fourier Transformation (FFT) in accordance with any known FFT algorithm.

16. The method of claim 13, wherein the circuitry generates the digital signals by calculating a Fast Fourier Transformation (FFT) in accordance with known FFT implementation.

17. The method of claim 13, wherein the circuitry generates the digital signals by creating a spectrogram having a spectrum of frequencies of the signal as it varies with time, and further detects an impulse prior to generating the digital signals that yields the spectrogram.

18. The method of claim 13, further comprising transmitting the captured acoustic data to a second location for storage or further processing.

19. The method of claim 13, wherein the circuitry generates the digital signals by creating a spectrogram having a spectrum of frequencies of the signal as it varies with time, and the method further comprises transmitting the spectrogram to a second location for storage or further processing

20. The method of claim 13, wherein the circuitry generates the digital signals by creating a spectrum of frequencies over a short period of time, and the method further comprises transmitting the spectrum to a second location for storage or further processing.

21. The method of claim 13, further comprising transmitting the captured acoustic data to a second location prior to the circuitry generating the digital signals that yields the spectrogram.

22. The method of claim 13, further comprising, responsive to a gunshot determination, recording at least one of a date and time of occurrence of the determination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] FIG. 1 is a schematic view of a system and method of gunshot detection in accordance with the present invention.

[0052] FIGS. 2-4 are, respectively, three spectrograms (44.1 kHz sampling rate, 250 kHz sampling rate, and 384 kHz sampling rate) and described in greater detail below. More particularly, FIG. 2 is a frequency analysis image that shows a frequency response, even including ultrasonic range (above 20 kHz) of an indoor gunshot computed over a 500 millisecond time span.

[0053] FIG. 3 is an image that shows a spectrogram of the same indoor gunshot. Blue indicates low energy, red indicates higher energy, and white indicates highest energy.

[0054] FIG. 4 is an image that shows a spectrogram of an indoor loud sound event (specifically, banging two boards together). The gunshot and boards share high energy across the audible spectrum, but the ultrasonic energy for the boards lasts a much shorter time.

DETAILED DESCRIPTION OF THE INVENTION

[0055] Referring to FIG. 1, a diagrammatic view of the present invention is shown generally at 10, wherein a first preferred stage includes monitoring for audio input that may capture a gunshot event. More specifically, a preferred embodiment includes apparatus that monitors or constantly scans for audio signals that may include the sound of a gunshot event. A first effort is made at this stage to filter our sounds that are decidedly not gunshot events, such as background noise. Higher level filters can be applied to identify possible gunshot like sounds. Thus, ultrasonic sensors, such as microphones, are appropriate for use to provide for “monitoring audio stream” at 1 in FIG. 1, and utilizes a device for converting sound waves into electrical signals (or digital information) that may then be amplified or recorded. A preferred microphone or sensor includes one that is capable of capturing and processing ultrasonic sound. The preferred embodiment may also include a filter that applies rules to isolate possible gunshot sounds. Such rules are known to the person of ordinary skill in art.

[0056] It is to be further understood that the apparatus 1 may be placed in various locations, either fixed or mobile. For example, a smartphone may be provided with a microphone that is able to capture gunshot sounds. A smartphone (or other device) may also be provided with an accelerometer that monitors motion and/or orientation of the device. Thus, for example, the accelerometer can monitor the smartphone for motion spikes in any axis (X,Y or Z) that could indicate that the device has hit a hard surface so that the sound associated therewith is not determined to be a gunshot. A preferred embodiment further includes the application of motion filtering rules 4 to identify device falls and hits on hard surfaces that might generate a gunshot-like sound with a high energy level at the microphone. In such a case where the device is mobile or otherwise provided with an accelerometer, both factors are applied 5 to determine if a Spectrogram waveform analysis should be performed (i.e., stage 2).

[0057] A second stage of the present invention expressly includes a consideration of ultrasonic sound waves. More particularly, a Spectrogram analysis 6 of the information captured by monitoring the audio stream, is performed. The resulting pattern is evaluated at a high level 7 to determine if a gunshot has been detected. More particularly, the present invention contemplates that a spectrogram of the potential gunshot sound is prepared such as that shown, for example, in FIG. 2. That spectrogram of the potential gunshot sound can be compared to known spectrograms representing the waveforms of the captured known gunshots. That comparison would include a consideration of ultrasonic frequencies. In so doing, the comparison will reveal (by similarity of the captured sound spectrogram to known gunshot spectrograms) whether the captured sound was that of an actual gunshot within a certain reliability range. The comparison includes ultrasonic frequencies of between 20 kHz and 150 kHz. By use of the ultrasonic range, the present invention reduces or minimizes false negatives and false positives.

[0058] The present invention also utilizes the fact that a gunshot exhibits a high energy response across an entire frequency band, albeit for a brief time, and utilizes spectrograms to look at more than signal intensity and frequency response. Where prior art devices have considered frequency and intensity for a discrete time period (see, for example, the '845 Patent), the present invention considers sonic and ultrasonic frequency response over a greater period of time without averaging across the entire period of time. The spectrogram analysis of the present invention differs from signal energy/intensity analysis of the prior art and thus allows for detection of a gunshot in both open and continued environments. More particularly, the preferred spectrogram of the present invention provides information regarding time (x-axis), frequency (y-axis) and intensity (e.g., high energy; z-axis). As shown in the “Frequency Analysis” image shown in FIG. 3, a frequency response includes ultrasonic range (above 20 kHz) of an indoor gunshot computed over a 500 millisecond time span. This seems to indicate that there is little to no high energy sound in the ultrasonic range, especially in the very high frequency range (EHB—will need to see this “Frequency Analysis”, and the next, images to verify that that is what it indicates). The image of FIG. 4 however shows that that high energy is in fact extant, but fleeting. Analyzing the frequency response of a 500 millisecond time window fails to reveal the ultrasonic information unique to a gunshot. FIG. 4 shows a spectrogram of the same indoor gunshot (blue indicates low energy, red indicates higher energy, and white indicates highest energy). FIG. 4 thus shows the characteristic of a gunshot, namely, high energy in the ultrasonic frequency range for a somewhat extended period of time (around 100 milliseconds from 0.10 to 0.20). FIG. 5 shows a spectrogram of an indoor loud sound event (specifically, banging two boards together). The gunshot and boards share high energy across the audible spectrum, but the ultrasonic energy for the boards lasts a much shorter time.

[0059] The present invention further includes looking at a larger time period than that known to exist in the prior art. Thus, by virtue of the spectrogram, the present invention considers high energy (i.e., loud) sounds of more intensity than the prior art, and further considers such factors for a greater length of time and in smaller increments than that previously accomplished in the prior art, at both sonic and ultrasonic levels. Thus, for example, where a prior art detection method may have considered results over 250 or 500 milliseconds, the present invention addresses time increments in as little as 100 milliseconds (0.1 sec) and considers the spectrogram information (time, frequency, intensity) for substantially the entire length of the captured gunshot sound—as much as a full second or more. Thus, under the present invention, key distinguishing energy readings are found in the first 100 milliseconds, but not averaged into a larger time period (such as 200 milliseconds) where the results would be averaged out and potentially missed.

[0060] If the above-described spectrogram comparison of the captured gunshot to a known gunshot spectrogram reveals an actual gunshot, that information my be relayed to third parties such as law enforcement, first responders, etc. Further, that information is preferably captured, and the spectrogram and sound profile is transferred to an AI engine 9, where the profile is added to the stored profiles, thus allowing for further comparison and further reduction or minimization of “false positives” and “false negatives.”

[0061] To the extent possible, further metadata such as distance from the microphone and gun type and caliber 10 are determined by Spectrogram Signature Pattern Analysis and Correlation, Pixel Array Histogram Correlation, AI Model edge processing, or other means. Once a gunshot event 10 is confirmed, gunshot metadata is published 11 to a metadata repository 12 for audit trail and chain of custody reporting. In the case of a BodyWorn camera, Video Recording 13 is started. Gunshot detection event notifications 14 are sent to Central Dispatch and any other predetermined authorized metadata recipients. To the extent possible, video, audio, and metadata is lived streamed to authorized recipients.

[0062] The Gunshot Detection closed loop process continues while the Gunshot Detection device is operational.

[0063] ADVANTAGES OF THE PRESENT INVENTION

[0064] The present invention will increase active-shooter real-time situational awareness both outside and inside buildings, while minimizing the negative effects of Gunshot Detection False Positives and False Negatives. Real-time edge processing and correlation of metadata from multiple sensors can correctly identify gunshot events that audio only gunshot energy or triangulation analysis would miss.

[0065] Information rich Spectrogram result signature patterns can uniquely identify metadata beyond whether a gunshot occurred. The signature pattern can further identify gun type, caliber, and distance and angle from the gun barrel.

[0066] The present invention provides highly accurate real-time situational awareness reporting from inside schools, offices, shopping malls, and other inside locations where legacy outside sound triangulation systems can't. At the same time, the Spectrogram analysis provides a high degree of gunshot recognition capability outside in clear air. In both cases First Responders are able to respond faster and more effectively to an active shooter event.

[0067] “Crowdsourcing” gunshot sensor data from multiple devices located in a school, church, synagogue, campus and other locations further increases the range and accuracy of real-time situational awareness reporting. The risk of “Friendly Fire” tragedies can be reduced, and situations can conclude sooner.

[0068] Having thus described exemplary embodiments of the present invention, those skilled in the art will appreciate that the within disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention. Accordingly, the present invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.