System and device for nearfield gunshot and explosion detection

• US 10,054,576 B2
• Filed: 08/21/2015
• Issued: 08/21/2018
• Est. Priority Date: 08/29/2014
• Status: Active Grant

• Current Assignee: FAB 5 Holdings LLC
• Original Assignee: Tracer Technology Systems Inc.
• Inventors: Overcast, Allan Ward
• Primary Examiner(s): Caputo, Lisa
• Assistant Examiner(s): Devito, Alex
• Application Number:
  US14/832,975
• Publication Number:
  US 20160209390A1
• Time in Patent Office: 1,096 Days
• CPC Class Codes: G01N 33/227 Explosives, e.g. combustive properties thereof detecting explosives in air G01N33/0057
• CPC Class Codes: G08B 13/1672 using sonic detecting means, e.g. a microphone operating in the audio frequency range
• CPC Class Codes: G08B 25/016 Personal emergency signalling and security systems emergency non-personal manually actuated alarm activators G08B25/12
• CPC Class Codes: G08B 29/188 Data fusion; cooperative systems, e.g. voting among different detectors
• CPC Class Codes: H04R 29/004 for microphones H04R29/007 takes precedence

Abstract

A computer-implemented system for nearfield gunshot and explosion detection comprising a hardware device with a differential air pressure sensor, a pressure amplifier that amplifies pressure signals generated by the differential air pressure sensor, a microphone, a microphone amplifier that amplifies audio signals generated by the microphone, and a pulse counter that calculates a total event length. The system includes a digital processor that processes the amplified signals from the differential air pressure sensor and the microphone and a data radio that generates alerts based on input from the differential air pressure sensor and the microphone. The system determines whether a gunshot event or an explosive event has occurred based on a pressure length sensitivity setting, a microphone length sensitivity setting, and a correlation sensitivity setting.

Claims

1. A computer-implemented system for nearfield gunshot and explosion detection comprising:

(a) a hardware device comprising a differential air pressure sensor that is configured to measure increases in air pressure that happen when a gun is fired or an explosive device is detonated, a pressure amplifier that amplifies pressure signals generated by the differential air pressure sensor, a microphone, a microphone amplifier that amplifies audio signals generated by the microphone, and a pulse counter that calculates a total event length;

(b) a digital processor that processes the amplified signals from the differential air pressure sensor and the microphone; and

(c) a data radio that generates alerts based on input from the differential air pressure sensor and the microphone;

wherein the system determines whether a gunshot event or an explosive event has occurred based on a pressure length sensitivity setting, a microphone length sensitivity setting, and a correlation sensitivity setting;

wherein the system is configured to differentiate between a gunshot and a non-gunshot explosive event by measuring the duration of the pressure event and the duration of the microphone event;

wherein if the pressure event is longer than 240 mS and the microphone event is longer than 400 mS, the system determines that a non-gunshot explosive event has occurred;

wherein the system is configured to differentiate between a single gunshot and multiple gunshots by generating an initial gunshot report, incrementing a gunshot counter, and starting a multiple gunshot window timer to determine whether more than one gunshot occurs during a preset period of time; and

wherein the system is configured to generate a first type of alert in the event of a single gunshot and a second type of alert in the event of multiple gunshots.

2. The system of claim 1, wherein the amplified pressure signal is transmitted to a first hardware-based root mean square detector circuit that generates a first voltage output that is transmitted to a first hardware-based envelope detector that converts the first voltage output to a first digital square pulse that is transmitted to the digital processor;

and

wherein the amplified audio signal is transmitted to a second hardware-based root mean square detector circuit that generates a second voltage output that is transmitted to a second hardware-based envelope detector that converts the second voltage output to a second digital square pulse that is transmitted to the digital processor.

3. The system of claim 1, wherein when the device is powered, it undergoes a calibration process wherein the device reads a first sequence of analog microphone readings, average the readings, and notes a default baseline microphone audio level reference;

wherein an internal tone generator within the device generates a tone and reads a second sequence of microphone readings and averages the readings to determine a reference level change with and without a tone present; and

wherein if the microphone calibration process is successful, an initialization message is sent to an alerting server, and all system variables are reset.

4. The system of claim 1, wherein an interrupt request process is initiated by a manual button push, a pressure-detected event, or a microphone-detected event;

wherein the system identifies a first-to-occur event by determining whether the manual button push event, the pressure-detected event or the microphone-detected event occurred first and sets a flag based on the first-to-occur event; and

wherein the system determines whether the manual button push event, the pressure-detected event and the microphone-detected event are inactive, and if so, calls event processing.

5. The system of claim 4, wherein the pressure-detected event has a length, the microphone-detected event has a length, and the system determines whether the length of the pressure-detected event exceeds a first predetermined value and whether the length of the microphone-detected event exceeds a second predetermined value;

and

wherein the system identifies either the pressure-detected event or the microphone-detected event as a last-to-deactivate event, and wherein the system determines the total event length based on activation of the first-to-occur event and deactivation of the last-to-deactivate event.

6. The system of claim 5, wherein if the pressure-detected event occurs before the microphone-detected event, the system determines whether the microphone-detected event occurred within a predetermined period of time after the pressure-detected event occurred;

and

wherein the system determines whether the length of the microphone-detected event is longer than the length of the pressure-detected event; and

wherein the system determines whether a gunshot or an explosion occurred based on the length of the microphone-detected event and the length of the pressure-detected event.

7. The system of claim 5, wherein if the microphone-detected event occurs before the pressure-detected event, the system determines whether the pressure-detected event occurred within a predetermined period of time after the microphone-detected event occurred;

wherein the system determines whether the length of the microphone-detected event is longer than the length of the pressure-detected event; and

wherein the system determines whether a gunshot or an explosion occurred based on the length of the microphone-detected event and the length of the pressure-detected event.

8. The system of claim 1, wherein the differential air pressure sensor is a subsonic sensor.

9. The system of claim 1, wherein the hardware device further comprises an absolute air pressure sensor.

10. The system of claim 1, wherein the hardware device further comprises an accelerometer sensor.

11. The system of claim 1, wherein the hardware device further comprises a location receiver.

12. The system of claim 1, wherein the hardware device further comprises a manual alert button.

13. The system of claim 1, further comprising a gunshot counter that determines the number of gunshots detected within a window timer period.