Sniper Localization System Marko Gasic Sandeep Brar Ehsan Dallalzadeh Balraj Mattu
Jan 22, 2016
Sniper Localization System
Marko Gasic Sandeep Brar
Ehsan Dallalzadeh Balraj Mattu
Overview Introduction Vision System Description Test Results Obstacles Encountered Project Finances Production Cost Conclusion Questions?
Introduction Snipers are a serious threat in urban warfare
environment. Civilian threat in cases such as Washington DC
sniper. Snipers are very effective at harassing and
impeding military operations. AcousticShield Designs system enables identification of
direction of origin of a sniper shot within seconds of the event.
System Overview
Vision
Existing Products• Above $15,000 US• Available only to elite military divisions and
not standard equipment to regular units or police forces
Acoustic Shield System• System cost around $2000• Low cost enables local police departments
and regular military units to purchase system
System Description
Functional Breakdown• Signal Acquisition• Gunshot Recognition• Delay Detection• 3-D Triangulation• Human-Machine Interface (H.M.I)
Principle of Operation• Sound waves reach 4 speakers at different times• Using these delays we can calculate the origin of
sound
Sound Acquisition
PC Hardware• M-Audio Delta 44 PCI audio card• 4/4 mono analog input/output channels• 24bit, 8kHz – 96kHz independent channel sampling• Winsound interface drivers
Sound Acquisition
Microphones• Electret Omni-directional condenser microphones.• -45dB sensitivity• 20Hz – 16kHz Frequency Response• 60 dB S/N ratio
Sound Acquisition
Microphone Preamplifier• Supplies minimum voltage required for microphone
operation• Amplifies signal to 500mV swing, compatible for PC
soundcard input.
Sound Acquisition Software
Sample at 44kHz
Continuously sample microphone inputs
When sample exceeds 0.2V, record next 1.0 seconds and place in memory
Recognition Algorithm
Understanding the characteristic of a gun shot
Time Domain Representation
Recognition Algorithm
Frequency Domain Representation
Recognition Algorithm
Algorithm is based on comparison of average power between two bins:
228 Hz (±150 Hz) 1 kHz – 1.5 kHz
Average Power
Average Power
11Bin1 average powerBin2 average power
Recognition Algorithm
Refinement after experimentation Needed to consider all 4 input at the
same time
Microphone
Sound Wave
Back
Distortion in frequency spectrum is introduced
Recognition Algorithm
Simple Solution
Analyze all four microphones
Accuracy is demonstrated in Test Results section
Δt Extraction 4 similar signals, out of phase Use Cross Correlation to determine phase difference
Δt14
Δt13Δt12
3-D Triangulation Extrapolate origin of sound using the 3 Δt’s and speed of
sound as input Use Gauss-Newton method to
solve 4 non linear equations
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tcazzyyxx
tcazzyyxx
tcazzyyxx
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Recover the X Y and Z coordinates of signal origin
Normalize vector to give azimuth and elevation angles
Easy to Use/Navigate Targeted towards Army Personnel Displays Azimuth and Elevation No installation Required
User Interface
Testing The testing was done in 2 phases:
• Testing for the detection in 2-D (X,Y)• Testing for detection of the elevation
Procedure A:• The system was setup• The software was running• Located the tripod at the center of a large circle • Drew a 2-D coordinate system about the center of the tripod • Marked the imaginary circle around the center of the tripod with points each about 30 degrees apart• Ran the sound sample of the gunshot twice at each point
Testing
• Recorded the Average, Trigger, X and Y values• Took a string from the sound source(speaker) to the
center of the tripod• Chose a point on the string and recorded its X and Y
components.• At the end, had pairs of vectors in 2-D
• Comparison Stage……• Wrote a C++ code to input each pair of vectors to
calculate the angle between the actual vector and the result vector from the system in Degrees
Observations
On average, the angle difference was about
2.78 Degrees
The accuracy was almost the same for all the
points in the surrounding
Testing cntd. Procedure B (Elevation):
• The system was setup• The software was running• Located the tripod at the center of a large circle • From points 90 Degrees apart, got samples • At each point, tried 3 different elevations: 1) above the center plane 2) at the same plane 3) below the center plane • Recorded the elevation that the program gave for each
trial• For each point, measured the elevation angle compared
to the center of the tripod (+ if above the center, (-) if below the center)
Observations
On average, elevation difference was 3.15
Degrees
Functional Specifications stated maximum
allowable error of 10 degrees
Obstacles Encountered
Initially used Texas Instruments DSP• Insufficient inputs: unable to sample both stereo
codecs simultaneously• Insufficient resolution: TMSC320 C6711 main audio
codec samples at only 11kHz, we need a minimum of 44kHz
• Extremely poor user interface and non-existent (yet advertised) compatibility with MATLAB
Obstacles Encountered
Initial Algorithm Divide sampled input into smaller intervals Analyze smaller intervals in frequency domain
Power Spectrum of t0 – t1 Power Spectrum of t2 – t3
Input Signal
Obstacles Encounterd
Initial Algorithm Determine if it’s gun shot or not by comparing
with known spectrum
Known SpectrumPower Spectrum of t0 – t1
Positive Match
Obstacles Encountered
Algorithm was implemented in Matlab and Simulink
Main Recognition BlockRecognition Subsystem 1
Obstacle Encountered
Problems Unable to achieve desired speed Didn’t do well when tried with real input
(instead of a wave file)
Financial Aspects
Prototype Development Cost:
• TMSC320 Daughter Board $120.00• MATLAB RTW Documentation $ 35.00• Microphones and Pre-Amps $ 60.00• Miscellaneous Audio Cables $ 30.00• M-Audio Delta44 $220.00• Other $ 25.00
• TOTAL $490.00
Budget Estimate Initial cost estimate $2260.00 Actual cost $490.00 Significantly lower cost due to change in
platform Savings with no loss in performance We were able to borrow the tripod, saving
~$100
Manufacturing Costs Assuming 50 units/month Based on Digi-Key bulk pricing where available
ITEM COSTMicrophone $ 1.20Pre-Amp $ 6.00Tripod $ 80.00M-Audio Card $ 130.00Cables $ 20.00PC $ 600.00Total $ 837.20
Conclusion
Successfully Demonstrated Functional Concept
Demonstrated market value and ability to produce at reduced cost
Encountered problems and chose alternate solutions
Stayed within budget and timeline considerations
Thank You
Questions?