Sunday, May 17, 2009

Praxis: The Sound (and Flash) of Gun Fire from Downrange

Posted at by Lyle at UltiMAK is this entitled "The Sound of Gun Fire from Downrange." I posted a comment there that I append to his below.

Be certain to go to the site and watch the video. If you can, set up a means of similarly training yourself and your buddies to know the sounds and sights of small arms firing.

It is important to know these sounds (and to experience the light effects of weapons fired at night) if you wish to stay alive when the range goes two-way.


I've long been disgusted by Hollywood's portrayal of sounds. Sounds in space, sound traveling at the speed of light, and the ridiculous sounds of gunfire made up in a studio. Even the news services will often do a time-shift, to synchronize the sound of a distant event with the video even though anyone who's been alive long enough to understand what they're seeing on TV knows that sound and light travel at different rates. I just, do, not, get why TV and movie people have to screw up reality so much. Far from adding anything, it subtracts from the final product.

For example, I think the long delay in the sound of a distant explosion at Boomershoot makes the experience more awesome. It adds to the perception of enormity. The movie, "Band of Brothers" is an attempt to show it like it really was, and for the most part they seem to have done a good job. Not when it comes to sound editing though. Super-sonic bullets whiz by, "whoosh-whoosh, zip, zip" and so on, and of course the sound always travels at the speed of light. It's taking a serious subject and turning it into slapstick.

In the interest of universal understanding, I made this recording of .308 rifle fire from about 380 yards while setting up some rifles for Boomershoot. The camera is about 20 yards from the targets (yeah, I was holding the camera, but I was behind a hill from the gun and in radio communication with the shooter-- completely safe).

Each shot delivers multiple sonic effects or events. First is the "CRACK-hiss" (mini sonic boom) from the bullet. Take the sonic boom from a jet flying over, speed it up a few octaves, and you'll have about the same thing. That bit is interesting in that it does not come from the gun, but from the bullet. You have no sense of the direction from which the bullet came. Imagine standing in the water on the shore of a lake and feeling the wake from a passing boat on your legs. From that sensation alone, you have no idea of where the boat came from, and little or no information about its direction of travel. The bullet's wake, as sound, gives you no more information-- just a "snap" that seems to come from nowhere. Next is the sound of impact, which is only audible in the first shot in this recording. Then comes the "boom" from the muzzle blast, followed by the reverberation in the surrounding hills and trees.

Note that the reverb almost seems louder than the crack-boom. That's due to the AGC (Automatic Gain Control) circuitry, A.K.A. "compression" built into the camera. The initial crack drives circuitry into gain reduction, and the gain comes back up for the reverb. To get the relative levels of the events portrayed accurately, I'll have to take a full-range stereo recorder into the field on another day and use its un-compressed level mode. If you have some nice speakers (and pretty powerful, as the dynamic range is quite wide) you’ll hear it as if you were actually standing there.

Regular CD audio has a dynamic range of about 100dB, IIRC-- close enough. This recording isn’t all that bad, though. Crank up the volume, use good speakers, and boost the bass to get the full effect (the mini electret mic on the camera isn’t great for bass response);

My reply:

In 1942, the United States Army made a training film, of which I have a dubbed VHS copy, that illustrated this for soldiers. They covered the sound effects of weapons large and small on the battlefield from M1911 to 155mm howitzer, at all ranges -- origin, overhead, and impact area.

I have trained folks in this by positioning them behind a backstop during the daylight at a local range, and also by letting them experience night fire from downrange by firing semi-auto rifles of different types from a fixed rest (much like the wooden framework used in infantry training for overhead fire, although in this case they are standing to side so they can both see and hear weapons effects at one hundred yards).

Note: in the night firing you learn very quickly which so-called flash suppressors actually suppress flash.



ScottJ said...

This is one of the many benefits of competing in NRA Highpower and why my fat ass needs to drop some weight and get back into it.

In the pits at the Highpower range is where I got some experience of what it might be like to be under fire.

HPL said...

Mike, if you could get that old training video into digital format and up on the web, that would be a tremendous service.

Sean said...

When an instructor, I made my trainees linger on the safe side of a 30ft berm, downrange, on the "Close Combat Range, Live Fire" portion of their training. When questioned by the CO, as to what the hell I was doing still downrange with my platoon, when we could have been eating chow, I replied " Turning them into old men, sir". The old man sent me some chow, had my platoon retire for eats, and rotated the other three platoons in succession to my loc, with instructions to age them also. And having been on the recieving end of the burp gun boogie(Iraq and Afghan vets know just what I'm saying) more than once, it makes you bring everything sharply into focus, and you immediately grasp what is important, and what is bullshit. I am an old dog, but these are old tricks.

Anonymous said...

Ditto the Highpower (AKA "Known-Distance-Range" comment. Working the firing line, pulling target frames behind the berm, exposes you to the super-sonic cracks from .223, .308 (plus various 6mm and 7mm) calibres.

You can tell the difference!

And the crack of multiple, rapid fire rounds overhead is exciting.


ScottJ said...

Ditto the Highpower (AKA "Known-Distance-Range" comment. Working the firing line, pulling target frames behind the berm, exposes you to the super-sonic cracks from .223, .308 (plus various 6mm and 7mm) calibres.

You can tell the difference!

And the crack of multiple, rapid fire rounds overhead is exciting.
Yes, and one time at a cold match everyone was out on the road behind the pits in the warm sun and didn't hear the calls to the firing line over the radio.

It was amazing how quickly we were all able to move when those cracks started overhead.

straightarrow said...

Uh, Anonymous, when they're coming my way "exciting" only works if it encompasses scared as Hell.

Johnny Deceptively said...

I also get pretty upset at all the fake gunshots in movies.

The best gunfire sound effects I've heard were from the bank heist shooting scene in Heat, and that's because Michael Mann liked the original sound recording so much he decided to not add effects later.