However, people cannot hear the crack everywhere. Simplified textbooks show an eternal Mach cone. But what if the projectile hits the target? The shock-wave won’t just disappear. Let’s follow the evaluation of the truncated cone:
Along the path of the supersonuc projectile, the change in pressure propagetes outward by the speed of the sound. But you can har the crack only at the points of constructive interference.
But this is not an infinite cone. The green lines indicate the boundaries. These lines are perpendicular to the cone surface. Actually they are perpendicular cones.
Behind the rear green cone and in front of the frontal one: you cannot hear the crack.
I call them perpendicular boundary cones or anti Mach cones.
So, for example, if the shot comes from a window of north building - most possibly the interviewed people could not hear the crack.
I counted 19 or 20 frames. By 30 fps it is around 650 ms.
Given:
- Frame delay: 20 frames at 30 fps → 0.67 seconds
- Speed of sound: 343 m/s ≈ 1,125 feet per second
- Speed of sound≈375 yards/second
Step 1: Estimate distance
Distance=Time×Speed of Sound
Distance=Time×Speed of Sound =0.67×375≈251.25 yards
Conclusion (in yards):
The sound of the gunshot reached the microphone 20 frames (≈0.67 s) after the visible reaction. Since sound travels at approximately 375 yards/second, the minimum distance to the shooter is about 251 yards.
This is a lower bound, because the bullet would have arrived (or the flash would have been seen) before the sound.