System and device for nearfield gunshot and explosion detection

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.