OBSERVING VARIATION OF ACOUSTICAL CHARACTERISTICS OF SEVERAL COMMON FIREARMS IN A QUASI ANECHOIC ENVIRONMENT AT A HIGH SAMPLING RATE by Tushar Kanti Routh A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Electrical & Computer Engineering MONTANA STATE UNIVERSITY Bozeman, Montana August 2016 ©COPYRIGHT by Tushar Kanti Routh 2016 All Rights Reserved ii ACKNOWLEDGEMENTS First, praises and thanks to the God, the Almighty, for His showers of blessings to complete the research successfully. I would like to express my deep and sincere gratitude to my research supervisor, Dr. Robert C Maher, Ph.D., P.E., Professor, and Head, Department of Electrical & Computer Engineering, Montana State University, Bozeman, Montana, for providing the opportunity and invaluable guidance throughout this research. His dynamism, vision, sincerity and motivation have deeply inspired me. It was a great privilege and honor to carry out my work under his guidance. I am extremely grateful for what he has offered me not only as a mentor but also as a human being. I would also like to thank him for his patience, empathy, and most importantly, understanding me as a person. My Special thanks go to Prof. Steven Shaw for his support in gunshot recordings. I am extremely grateful to Angelo Borzino, for his support in the interpretation of recorded signals. I am extending my gratitude to Tyler Davis, for his assistance during the whole period. Finally, my thanks go to my parents and all my friends and staff of this department, who has directly and indirectly, supported me to complete the research work. iii TABLE OF CONTENTS 1. INTRODUCTION .......................................................................................................... 1 1.1 Introduction .............................................................................................................. 1 1.2 Motivation ................................................................................................................ 1 1.3 Broader Impacts ....................................................................................................... 4 2. LITERATURE REVIEW ............................................................................................... 5 2.1 Formation of Gunshot Wave .................................................................................... 5 2.2 Ground Reflection of Gunshot Signals .................................................................... 8 2.3 Defining Muzzle Blast Wave ................................................................................. 12 2.4 Calculating Total Energy from a Blast Wave ........................................................ 13 2.5 Significance of Anechoic Recording with High Sampling Rate ............................ 15 2.6 Calculating Muzzle Blast Duration ........................................................................ 18 3. METHODOLOGIES .................................................................................................... 21 3.1 Test Rig .................................................................................................................... 21 3.2 Recording System .................................................................................................... 25 3.2.1 Microphone Sensitivity ................................................................................... 27 3.3 Selection of Firearms ............................................................................................... 28 3.4 Determining the Muzzle Blast Duration .................................................................. 29 3.4.1 Muzzle Blast Duration by Waveform Observation ........................................ 29 3.4.2 Muzzle Blast Duration by Energy Accumulation ........................................... 29 3.5 Determining the Positioning of the Firearm for Each Shot ..................................... 30 3.6 Methodology Used for Calculating Acoustical Power from a Single Shot ............. 35 3.7 Correlation between Signals .................................................................................... 37 3.8 Comparing Experimental Recording with Real Life Gunshot Recordings ............. 38 3.9 Prediction of Gunshot Signal at a Particular Direction ............................................ 40 4. RESULTS ..................................................................................................................... 49 4.1 Colt 1911A1 (45 ACP) ............................................................................................ 43 4.1.1 Muzzle Blast Pressure Variation for Colt 1911A1 (45 ACP) ......................... 44 4.1.2 Position of the Firearm during 10 Shots of Colt 1911A1 (45 ACP) ............... 45 4.1.3 Muzzle Blast Duration of Colt 1911A1 (45 ACP).......................................... 46 4.1.4 Total Acoustic Energy Variation for Successive Shots of Colt 1911A1 (45 ACP) ................................................................................... 48 4.2 Glock 19 ................................................................................................................... 49 4.2.1Muzzle Blast Peak Pressure ............................................................................. 50 4.2.2 Position of the Firearm During 10 Shots of Glock 19/ 135JHP ..................... 51 4.2.3 Muzzle Blast Duration .................................................................................... 59 iv TABLE OF CONTENTS CONTINUED 4.2.4 Total Energy Variation from One Shot to Another ........................................ 53 4.3 Glock 23 ................................................................................................................... 54 4.3.1Muzzle Blast Peak Pressure ............................................................................. 55 4.3.1 Position of the Firearm during 10 Shots of Glock 23 ..................................... 56 4.3.2 Muzzle Blast Duration .................................................................................... 56 4.3.3Total Energy Variation from One Shot to Another for Glock 23 .................... 57 4.4 Sig 239 ..................................................................................................................... 59 4.4.1Muzzle Blast Peak Pressure of Sig 239 with 165 Gr Winchester Bullets .............................................................................. 69 4.4.2 Position of the Firearm during 10 Shots of Sig 239........................................ 69 4.4.3 Muzzle Blast Duration .................................................................................... 70 4.4.4 Total Energy Variation from One Shot to Another......................................... 72 4.5 Surgeon/AI ............................................................................................................... 64 4.5.1 Muzzle Blast Peak Pressure of Surgeon Rifle with 175 Gr Sierra Matchking® .................................................................................................... 65 4.5.2 Position of the Firearm during 10 Shots of Winchester 0.308 Caliber Rifle .......................................................................................... 65 4.5.3 Muzzle Blast Duration .................................................................................... 66 4.5.4 Total Energy Variation from One Shot to Another ........................................ 68 4.6 Stag Arms AR15 ...................................................................................................... 69 4.6.1 Muzzle Blast Peak Pressure of AR15 with 62 Gr Lake City .......................... 70 4.6.2 Position of The Firearm during 10 Shots of AR 15 Rifle ............................... 71 4.6.3 Muzzle Blast Duration .................................................................................... 72 4.6.3 Total Energy Variation from One Shot to Another ........................................ 74 4.7 CZ 452 (Ceska Zbrojovka) (.22 caliber) .................................................................. 75 4.7.1Muzzle Blast Peak Pressure ............................................................................. 76 4.7.2 Position of the Firearm during 10 Shots of 0.22 Caliber Long Rifle .......................................................................................... 77 4.7.3 Muzzle Blast Duration .................................................................................... 77 4.7.4 Total Energy Emission from 0.22LR .............................................................. 78 4.8 Ruger SP 101 .......................................................................................................... 89 4.8.1 Muzzle Blast Peak Pressure of Ruger SP 101 with 0.38mm Caliber Ammunition…………………………………………………………80 4.8.2 Position of the Firearm during 10 Shots of Ruger SP101 with 0.38 Caliber ............................................................................................. 81 4.8.3 Muzzle Blast Duration .................................................................................... 82 4.8.4 Total Energy Variation for Different Shots .................................................... 84 4.9 Ruger SP101 with 357 Magnums Ammunition ....................................................... 85 4.9.1 Muzzle Blast Peak Pressure of Ruger SP 101 with 0.357 inch Caliber Ammunition………………………………………..........86 4.9.2 Position of the Firearm During 10 Shots of Ruger SP101 with 0.38 caliber .............................................................................................