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Audio Chronograph

Printed From: Tippmann Paintball
Category: Tippmann Paintball
Forum Name: Paintball Ideas / News From Tippmann
Forum Description: Got a new idea or a way to improve something?
URL: http://www.tippmannsports.com/forum/wwf77a/forum_posts.asp?TID=157392
Printed Date: 09 May 2026 at 11:36am
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Topic: Audio Chronograph

Posted By: Olcaddy
Subject: Audio Chronograph
Date Posted: 14 July 2006 at 2:22am

    Ok guys I searched a bit and did not find anything related to this. I must admit that this is not originally my idea; I saw this somewhere in the bowels of the internet with regards to airsoft using two sheets of paper and two microphones. I have somewhat heavily modified it to paintball and simplicity.

    This method relies heavily on one - if not the - best free audio softwares available. You may download and read more about it http://audacity.sourceforge.net/ - here . The program has a very simple interface, play record pause etc., and a simple and useful highlighting and zoom feature.

    Now let’s get to the real point of this post. I like may people do not have a chrono but I recognize the need of one. This setup requires a microphone, laptop or long mic cord, paintball gun, tape measurer, and hard surface (tree, fence, car, 15th century Chinese vase, etc.) I chose a good distance from my chosen tree that I knew would allow me to easily stand in the same spot each trial, there happed to be 42' between my barrel and the tree, this number is important.

    I placed my mic halfway between my gun and the tree. Where you put your mic is not important as long as it is in line with you and the tree.

    Next just load up Audacity, hit record, get into position, and fire away. Not to fast. You don’t want more that one ball in the air at a time. When you are done shooting, 4 shots sounded nice to me, hit the spacebar on your computer (stops the recording). Hopefully you get something like this, minus the yellow highlight I added.
http://imageshack.us">

    First you see 4 sets of one big spike followed by one little spike. After that the jumble is a half hearted attempt to measure my bps. You want to zoom into one of the sets of spikes including a little extra like what is highlighted in my picture. Do this by clicking and dragging and pressing the http://imageshack.us"> button.

    This should give you something like this.
http://imageshack.us">

    Continue by highlighting as shown. I chose the second large spike because I figured it was closer to when the paintball actually left my barrel, and if it wasn't, it would result in a shorter time thus higher velocity, this may give you a reading for higher velocity than you are running which is not as dangerous as a thinking your velocity is lower than it really is.

    The time between spikes is easily found in the yellow highlighted section. My time was .185663 seconds. The ten thousandth place should be accurate enough for this exercise so for this calculation I would use .1857.

    Now you can’t just take distance over time here, 42/0.1856 would give me 226 fps and that just isn't right. So I had to unexpectedly take into account something else.

The speed of sound.
    So as we all know the speed of sound at sea level is 1,100 fps, I'm not sure how much it varies with elevation, humidity, and phase of the moon so I just used 1,100.

    Now to include the speed of sound we need to know how long it takes the sound to get to the microphone from its source. Now as long as your mic is inline with the gun and hard surface the time I need to subtract from my .1856 number is the time it takes sound to travel that entire distance. For me 42/1100 is .038181818 seconds. Again rounded to .0382. Your actual time will be .1856-.0382 or .1474 seconds.

    Finally distance over time is 42/.1474 or 284 fps. See how much the speed of sound matters. And this I feel is a good chrono substitute.

Now for things that I may need to consider

Over 42' drag will slow down the ball. To account for this we need the formula for the force of drag:

Force of drag = .5(Coefficient of friction)(density of air)(Affected Area)(velocity)²

Then to get the change in velocity you would need F=ma to find acceleration, next you need v = v₀ + (a)(t) and some maybe some calculus for point blank velocity.

Because of drag this is an average the fps will be higher than 284 at the barrel and lower than 284 at the tree.
I would like somone to check this against an optical chrono. I believe it is quite accurate.
Different guns/barrels/setups will give different shot spikes so be careful what spike you choose

About me
I was on the forum quite a lot 3 years ago, stopped paintballing for some reason. Luckily I'm back into it. Unfortunately my old member name was deleted. Not a big deal. My gun is in the sig, it suits my needs especially cost. I hope you find this as cool/useful as i did, even though it feels like a final for physics class

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Replies:

Posted By: DeTrevni
Date Posted: 14 July 2006 at 2:44am

I see where you're going with this, and it seems like a good idea, but I don't know how many people are going to mess around with all of that math!

I might have to try it out though...

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Evil Elvis: "Detrevni is definally like a hillbilly hippy from hell"

Posted By: Olcaddy
Date Posted: 14 July 2006 at 2:57am

Its not so bad, I could simplify it but I like people to have a grasp of things they use. I like people knowing how their gun works, how thier car works, and how their cool audio chronograph works. I may edit this post with a simple version with just distance and time as variables.

Oh and "Cadillac: Going fast with more class"

I have a 1969 Deville Convt.

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Posted By: DeTrevni
Date Posted: 14 July 2006 at 2:59am

Rollin' in a '65 Skylark Special. My pride and joy!

I demand pics of the Caddy!

Anyway, I'm afraid the sheer complexity might drive people away. Maybe you could add a shortened version at the end, just for the impatient out there.

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Evil Elvis: "Detrevni is definally like a hillbilly hippy from hell"

Posted By: Olcaddy
Date Posted: 14 July 2006 at 3:15am

Ok the simplest way I think I can get it is this.
If you read my first long post, in this formula D(Distance) for me was 42 feet, t(time) for me was 0.1856

fps = D/[t-(D/1,100)>

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Posted By: DeTrevni
Date Posted: 14 July 2006 at 3:21am

Which equals 284.904! That's cool.

However, you're shootin a bit hot there buddy!

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Evil Elvis: "Detrevni is definally like a hillbilly hippy from hell"

Posted By: pntbl freak
Date Posted: 14 July 2006 at 10:53am

284 isnt over at every field. I think its 290 or 300 limit at my field.

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Posted By: carl_the_sniper
Date Posted: 14 July 2006 at 11:31am

background noises could screw with it a bit.

cool formula gona have to try that

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<just say no to unnecessarily sexualized sigs>

Posted By: Olcaddy
Date Posted: 14 July 2006 at 11:41am

The shot and the splat show up as clear spikes as you can see. I did this outside of course so there was some wind/birds, no cars or roosters or anything loud but anyplace you would shoot off some rounds of paint should be quiet enough

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Posted By: carl_the_sniper
Date Posted: 14 July 2006 at 2:53pm

yeah i didnt think the background noise would really matter as long as nobody screams and you think its a paintball. 500fps wow

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<just say no to unnecessarily sexualized sigs>

Posted By: Monk
Date Posted: 14 July 2006 at 3:33pm

Not a bad idea, and reletively cheap. I could make a java based program to run the numbers and host it somewhere. Thats if I got around to it lol.

Posted By: You Wont See Me
Date Posted: 14 July 2006 at 3:39pm

You should compare it to what a chrono reads on it.

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Posted By: Ghost-Rider
Date Posted: 14 July 2006 at 4:06pm

if its accurate it would be sweet cause chronos cost wayyy to much !

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Posted By: Monk
Date Posted: 14 July 2006 at 4:44pm

Ok, figured out I dont have a compiler anymore, so I did it in javascript.

Its pretty much the same thing, but you guys have more work to do.

<html>
<body>
<SCRIPT TYPE="text/javascript">
//writen by Joshua Stuckey
var time = prompt('Time', 'Up to any decimal');
var distance = prompt('Distance', 'Distance from wall to gun');
var sof = distance / 1100;
var ntime = time - sof;
var fps = distance / ntime;
alert('Your fps is ' + fps);
</script>
</body>
</html>

Thats the code, just save it in a notepad or a text editor, as a .html file.

Then open file in any javascript enabled web browser. This code does not account for the drag, but when using under 20 feet, it shouldnt matter.

EDIT: working on a new one with a form interface, easy to read crap. hopefully I can get it hosted somewhere.

Posted By: Olcaddy
Date Posted: 14 July 2006 at 5:12pm

I like It works.

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Posted By: barn_user
Date Posted: 14 July 2006 at 7:50pm

Your too smart...share.

Posted By: Squishey
Date Posted: 15 July 2006 at 2:34am

this is really cool, however like a lot of other people you lost me in the math. (stupid math)

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Canadians do it on top.

Posted By: adblink
Date Posted: 15 July 2006 at 2:41am

this is pretty sweet, has anyone compared it to a real chrono?

also does it matter where the mic is placed between the target and the gun? as long as its under 20 feet and anywhere in the middle should be fine?

Posted By: Monk
Date Posted: 15 July 2006 at 3:02am

adblink wrote:

this is pretty sweet, has anyone compared it to a real chrono?

also does it matter where the mic is placed between the target and the gun? as long as its under 20 feet and anywhere in the middle should be fine?

Well, right now Im working on one to account for the drag, and to make it all look better.
But the mic can be at the tip of the gun barrel to the wall.

This is actually really fun, Ive been wanting to use this java for something. lol.

EDIT:
This version you dont have to reload the page to do another computation.

<html>
<body>
<SCRIPT TYPE="text/javascript">
//writen by Joshua Stuckey
function PaintBall()
{
var time = document.speed.time.value;
var distance = document.speed.dist.value;
var sof = distance / 1100;
var ntime = time - sof;
var fps = distance / ntime;
document.speed.fpsface.value = fps;
}
</script>
Place the microphone between the barrel and the wall, and record the time.
<form name="speed"><br>
Time:
<Input Type="text" name="time"><br>
Distance:
<Input Type="text" name="dist"><br>
<Input type="button" Value="Calculate FPS" onClick="PaintBall()">
<Input type="text" name="fpsface">FPS
</form>
</body>
</html>

There ya go dudes. All cleaned up. Still no drag, so its still only accurate to about 20ish feet. So add about 5fps.

Posted By: Silent
Date Posted: 15 July 2006 at 11:45am

That is so cool. But I won't be using it since I already have a chrony.
But thank you for the information. Good job.

-Silent

Posted By: pattison
Date Posted: 16 July 2006 at 1:20pm

If you shoot across the laptob/mic you should be able to forget mach correction. By shoot across, i mean pc at 5 metres, target at 10 metres.

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Posted By: Monk
Date Posted: 16 July 2006 at 3:39pm

pattison wrote:

If you shoot across the laptob/mic you should be able to forget mach correction. By shoot across, i mean pc at 5 metres, target at 10 metres.

I thought of that, but you still have to account for the distance from the gun to the mic and the wall to the mic. So its going to be the same as when the mic is right next to the barrel.

Posted By: pattison
Date Posted: 16 July 2006 at 3:52pm

I disagree, you want audacity to simulate "real time", but when the mic is on the barrel, the impact time is offset (sound delay). However when it is in the middle, both the muzzle sound and the impact sound are delayed by the same amount (assuming mic is in the middle). Think of it as +1/60sec correction for muzzle and +1/60sec for impact, cancelling each other out. It makes sense to me, correct me if I am wrong. All my method does is avoid a little math and put a laptop in the line of fire.

Really I am just talking out my a** here, it would be way more practical to have the laptop at the same place as the gun. If you use sheet metal as a target you can be sure to get a good sound footprint at 5-10m so there would be no advantage to having mic in the middle.

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Eat The Brisket

Posted By: Monk
Date Posted: 16 July 2006 at 4:00pm

pattison wrote:

I disagree, you want audacity to simulate "real time", but when the mic is on the barrel, the impact time is offset (sound delay). However when it is in the middle, both the muzzle sound and the impact sound are delayed by the same amount (assuming mic is in the middle). Think of it as +1/60sec correction for muzzle and +1/60sec for impact, cancelling each other out. It makes sense to me, correct me if I am wrong. All my method does is avoid a little math and put a laptop in the line of fire.

Na, you have to account for sound traveling faster than the ball coming at you, then the speed of sound after it hits the wall. So essentially, the speed of sound is still factord for the total distance. doppler affect does screw things up a bit, that why Id rather just put the mic next to the barrel.

Posted By: Olcaddy
Date Posted: 16 July 2006 at 4:57pm

My mic was in the middle of the line of fire. The sound of both the shot and splat take time to get to the mic, they both make the length of the shot seem longer. They do not 'cancel out'. Wherever the mic is you will need to subtract the time it takes sound to travel the entire distance of your shot from your measured time.

Monk wrote:

doppler affect does screw things up a bit, that why Id rather just put the mic next to the barrel.

I believe that doppler effect only matters if you are interested in the sound that the ball (or any object) makes while it is moving relative to the mic. The only sounds were are interseted im are not(tree and gun.)

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Posted By: pattison
Date Posted: 16 July 2006 at 5:37pm

Olcaddy wrote:

My mic was in the middle of the line of fire. The sound of both the shot and splat take time to get to the mic, they both make the length of the shot seem longer. They do not 'cancel out'. Wherever the mic is you will need to subtract the time it takes sound to travel the entire distance of your shot from your measured time... The only sounds were are interseted im are not(tree and gun.)

Naw, think about it, if your mic really was at the halfway point of the trajectory, consider this:
You pull trigger: this is +0seconds
audacity "hears" you fire: happens at t+.017sec (assuming ~5m GUN dist to mic)
actual impact: +.1sec
audacity hears impact: +.117sec (assuming 5m TARGET dist to mic)
Total flighttime: Actual= 0.1-0 =0.1 Audacity= 0.117-0.017 =0.1
If the mic is equal distance from the gun and target speed of sound time gets cancelled out, I promise.
Alright, this is my last post, I've got to try to keep physics to myself. Hope noone tries to tell me that cockers shoot farther.

Edit: And yeah, doppler applies when waves are emitted from an object that is moving relative to you.

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Eat The Brisket

Posted By: Monk
Date Posted: 16 July 2006 at 6:20pm

Doppler would matter if we worried about pitch, does that count. lol

Ok, I think I see what your saying. But audacity wouldnt hear it at +.117, it would hear it at +.134. because the need to account for the time it takes sound to get to you after the impact.

Posted By: SSOK
Date Posted: 16 July 2006 at 8:42pm

This is a great idea, If you had a VERY simple program set out for this you could probably market it somehow. The only problem with this is that, People are Idiots. You are smart. If the majority of the paintball world used this method it would be a disaster though, due to the complexity.

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Posted By: cardboardninja
Date Posted: 18 July 2006 at 7:15pm

If the mic is exactly in the middle, you will not have to account for sound.

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Posted By: Olcaddy
Date Posted: 18 July 2006 at 9:05pm

cardboardninja wrote:

If the mic is exactly in the middle, you will not have to account for sound.

At first I did not believe that this was true. However, after looking into it a bit I now agree. From now on when I use this method I will place the mic at the gun and use the simple formula to account for sound. I still would greatly appreciate anyone with a chronograph to compare this method.

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Posted By: pooperscooper
Date Posted: 18 July 2006 at 10:05pm

This is awesome. I love physics.

*goes to buy mic*

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Posted By: Olcaddy
Date Posted: 18 July 2006 at 11:33pm

pooperscooper wrote:

This is awesome. I love physics.

*goes to buy mic*

Well just to let you know if you have some headphones you can use them as a mic. Trust me, or try it yourself, just plug your headphones into the mic port. The sound will not be as clear as with a mic and quality varies depending on the headphones. I would suggest putting the headphones by the splat because they may not pick up the quieter sound from far away. I would reccomend a mic but this method works in a pinch and is better than shooting hot.

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Model 98
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My edits are in red

Posted By: Monk
Date Posted: 19 July 2006 at 1:52am

Ugh, i need to take a break. Between my accounting of my checkbook in my head, and trying to figure out why my generator wont recharge the bugs battery. My brain is fried.

Ill attempt to understand all this whoha some other time. For now, I concede defeat. lol.

But the idea for the chrono still remains...Kickass.

Posted By: usafpilot07
Date Posted: 25 July 2006 at 2:56pm

Our PACT Timer does something like this. Normally they just measure the amount of time between each shot to calculate the BPS of your gun. But some of the higher-end ones also give you the velocity of he gun you're check. I know it's not a chrono because you can do it at a distance. So, even though you have a really good thought, I think it's unfortunetly already been taken.

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