i tried to read the eleven pages, to be honest, I do not know enough about it, to understand it fully. But what I understood is that there was an incident in the West Bank, where someone was shot and in this paper there are sound waves of shot rows to be seen.... I do not see anything similar to what Lookoutfacharlie showed.
The main points are on pages 2 to 3. They describe the audio signatures of gunfire. These include:
1) the muzzle blast:
A conventional firearm uses a confined combustion of gunpowder to propel the bullet out of the gun barrel. The hot, expanding gases rapidly pressurize the chamber behind the bullet. The pressure accelerates the bullet down the gun barrel and out the muzzle, accompanied by the jet of combustion gas emitted from the muzzle, the muzzle blast. The muzzle blast sound propagates in all directions, but much of the acoustic energy is expelled in the general direction the gun barrel is pointing. The muzzle blast comprises an acoustic shock wave and a brief, chaotic sound lasting only a few milliseconds [5-7].The muzzle blast sound propagates through the air at the speed of sound (e.g., 343 m/s at 20°C), and like any sound, the acoustic waves interact with the surrounding ground surface, obstacles, temperature and wind gradients in the air, spherical spreading, and atmospheric absorption. A recording microphone located at some distance from the firearm will receive the muzzle blast sound accompanied by multi-path reflections and reverberation. If the direct sound path from the firearm to the microphone is obscured by terrain, buildings, or other obstructions, the received muzzle blast consists only of diffracted and reflected sound [5, 8-10].
2) the shock wave phenomenon:
An object traveling through the air at a rate faster than the local speed of sound creates a ballistic shockwave. Once launched, the shock wave itself moves through the air at the speed of sound. A supersonic projectile that travels through the air creates a shockwave cone that trails behind the bullet’s path [5, 7, 8]. ...
A microphone located near the trajectory of a supersonic bullet will detect the shock wave immediately after the bullet passes by. The time of arrival of the shock wave at the microphone depends on the distance of the microphone from the bullet’s path and the Mach number of the bullet. [In other words, the closer the microphone to the bullet, the quicker it will pick up the sound.]
3) relative timing of shock wave and muzzle blast:
When a firearm shoots a supersonic bullet, the bullet’s ballistic shock wave emanates from the bullet’s path as the bullet travels down range faster than the speed of sound, while the muzzle blast of the gun propagates at the speed of sound. This means that the sound of the ballistic shock wave will precede the sound of the muzzle blast at points down range near the bullet’s path.
The paper then presents a case study on how these facts can be used in a forensic investigation to estimate the approximate distance a rifle was fired from a camera that picks up both the ballistic shock wave and the muzzle blast. In the example from the West Bank, the audio shows the initial sound of the shock wave followed by the muzzle blast approx. 310 ms later, as well as what look like some reverberations or echoes.
He says in this very video, that he had listened to more than 170 of those shots with this caliber, and he is a sound specialist, does that for years ans years.
The vast majority of recordings of gunshots, e.g. on YouTube, are recordings taken from close to the rifle, either to the side or behind it. Recording from that location will not pick up the ballistic shock wave. To get that on audio, the camera/microphone needs to be in the path of the bullet, in front of the rifle, and not behind the target. This guy doesn't seem to be aware of that.
So can you explain me, what that second sound is, if its not found in any other "shot sound wave image or sound" (I am german, I know it sounds clumsy)? Or what did I or he get wrong?
The first sound is the ballistic shock wave, which reaches the camera almost instantly as the bullet passes next to, or above, the camera faster than the speed of sound. The second sound is the muzzle blast, which travels much slower, at the speed of sound. The two sounds are the sound of the bullet breaking the sound barrier, and the sound of the explosion cause within the rifle when the bullet is fired. The reason there are two sounds is that they have two different sources, separated in time. It takes a fraction of a second for the sound of the muzzle blast to "catch up" to the bullet.
The sound he analyzes is from the ground, not from the shooters place. I really do not get your point here, I am sorry...
Yes, that is why the recording picks up both the shock wave and the muzzle blast. In the example of a .30-06 that he uses as a comparison, there is only one sound, the muzzle blast, because whoever recorded that sound was probably recording from very close to the shooter's position, not in the path of the bullet. If he had used a recording of a .30-06 where the camera was located somewhere along the path of the bullet, he would see 2 sounds: the shock wave and the muzzle blast.