# Audio Chronograph



## Hagencopen (Mar 4, 2011)

Has anyone ever played with this method? My results cannot possibly be accurate. Double thera black( 9in x 1 in non tapered) reveals ~ 90 fps, SINGLE thera gold( same dimensions as black for this) was ~ 110 ! I know these numbers are off. I am assuming its the method of recording, but with this program, Audacity , you are able to pinpoint release point and impact point to the 5h decimal place. I was just curious if anyone else has played with this method. I'll post detailed results if people are interested.


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## PandaMan (Oct 14, 2010)

Hagencopen said:


> Has anyone ever played with this method? My results cannot possibly be accurate. Double thera black( 9in x 1 in non tapered) reveals ~ 90 fps, SINGLE thera gold( same dimensions as black for this) was ~ 110 ! I know these numbers are off. I am assuming its the method of recording, but with this program, Audacity , you are able to pinpoint release point and impact point to the 5h decimal place. I was just curious if anyone else has played with this method. I'll post detailed results if people are interested.


How exactly are you doing it? Just the point of release and the point of impact, with s = d/t? If you are doing that, there shouldn't be anything wrong. Are you sure you did the calculations correctly? 1 millisecond is 0.0001 seconds so say if it was 600 milliseconds between the two and it was at 5 meters, it would be 5 divided by 0.06 which equals about 83m/s, which is 272 fps. I predict you messed up with the milliseconds.

PS what ammo are you using? Have you forgotten to convert to fps and accidentally left it as m/s?


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## slingshot_sniper (Feb 20, 2011)

How do you use this thing?


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## Hagencopen (Mar 4, 2011)

PandaMan said:


> Has anyone ever played with this method? My results cannot possibly be accurate. Double thera black( 9in x 1 in non tapered) reveals ~ 90 fps, SINGLE thera gold( same dimensions as black for this) was ~ 110 ! I know these numbers are off. I am assuming its the method of recording, but with this program, Audacity , you are able to pinpoint release point and impact point to the 5h decimal place. I was just curious if anyone else has played with this method. I'll post detailed results if people are interested.


How exactly are you doing it? Just the point of release and the point of impact, with s = d/t? If you are doing that, there shouldn't be anything wrong. Are you sure you did the calculations correctly? 1 millisecond is 0.0001 seconds so say if it was 600 milliseconds between the two and it was at 5 meters, it would be 5 divided by 0.06 which equals about 83m/s, which is 272 fps. I predict you messed up with the milliseconds.

PS what ammo are you using? Have you forgotten to convert to fps and accidentally left it as m/s?
[/quote]

Yep, find the point of release, and the point of impact, find the difference, and divide by distance. It must be my calculations, although im not sure how. I have not even considered the millisecond conversion. An example of one reading would be release @ 24.35026 seconds , impact @ 24.4225, the difference is .07224 seconds, at 9 feet. This equates to ~ 125 fps, which cannot be correct.

I'm using 3/8 steel.

Why would i need to consider the millisecond conversion?


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## PandaMan (Oct 14, 2010)

Hagencopen said:


> Has anyone ever played with this method? My results cannot possibly be accurate. Double thera black( 9in x 1 in non tapered) reveals ~ 90 fps, SINGLE thera gold( same dimensions as black for this) was ~ 110 ! I know these numbers are off. I am assuming its the method of recording, but with this program, Audacity , you are able to pinpoint release point and impact point to the 5h decimal place. I was just curious if anyone else has played with this method. I'll post detailed results if people are interested.


How exactly are you doing it? Just the point of release and the point of impact, with s = d/t? If you are doing that, there shouldn't be anything wrong. Are you sure you did the calculations correctly? 1 millisecond is 0.0001 seconds so say if it was 600 milliseconds between the two and it was at 5 meters, it would be 5 divided by 0.06 which equals about 83m/s, which is 272 fps. I predict you messed up with the milliseconds.

PS what ammo are you using? Have you forgotten to convert to fps and accidentally left it as m/s?
[/quote]

Yep, find the point of release, and the point of impact, find the difference, and divide by distance. It must be my calculations, although im not sure how. I have not even considered the millisecond conversion. An example of one reading would be release @ 24.35026 seconds , impact @ 24.4225, the difference is .07224 seconds, at 9 feet. This equates to ~ 125 fps, which cannot be correct.

I'm using 3/8 steel.

Why would i need to consider the millisecond conversion?

[/quote]
Ah ok, I thought the timer would just measure it in milliseconds rather than decimals of seconds (if you get what I mean).

I see your problem. The only thing I can suggest is do it at a longer distance? Maybe 5 meters (16ft) like in my example in the last post.

Also are you sure the timing is accurate?


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## Hagencopen (Mar 4, 2011)

The timing is negotiable, but cant be off more than a few milliseconds, the trick with this is to find the exact audio peak where the release is, and then again at impact.

I think a longer distance is a good suggestion, it will be easier to isolate the peaks in the audio and give a cleaner reading overall.

Good Suggestions PANDA !

Still a little baffled.


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## Hagencopen (Mar 4, 2011)

slingshot_sniper said:


> How do you use this thing?


Use an audio recording program that can be analyzed to a deep degree, IE Audacity. Pinpoint the release point, and impact point, and find the difference between the two, divide by distance. This should reveal the speed( m/s ft/s, whatever). Rudimentary guide


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## Bill Hays (Aug 9, 2010)

One thing you'd need to be sure of is that the microphone is exactly in middle. 
another way to do it is to have two sheets of paper a certain distance apart with the microphone exactly equidistant. Shoot through the two sheets of paper to give a distinct sound signature for each strike.


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## Henry the Hermit (Jun 2, 2010)

I use this method, with Audacity, and my measurements are pretty consistent with what others get with chronys. Your math is correct, but it appears your method of measurement is inaccurate. The trick is in determining the exact time between two points of flight. It is almost impossible to determine the exact time of release. I shoot from a minimum distance of 5 feet behind the 9 inch paper plate target placed exactly 10 feet from my hanging cloth backstop. If I get closer to the target, it can be difficult to separate the sound of release from the sound of the ball striking the target.

Refer to the graphic below. The first waveform is the release, and as can be seen, it is not easy to determine what is the exact point of release. The second waveform, at ~18.802 is the ball striking the paper plate. The third waveform at ~18.855 is the ball striking the backstop. In both cases it is quite easy to determine the exact time of impact. I expand each waveform to the point that I can determine the exact point of impact to three decimal places, then simply subtract the paper plate point from the backstop point. In this case, elapsed time is .053 seconds, or 53 msec. To convert to fps divide 1 by .053 and multiply by distance traveled. IOW 1/.053=18.87*10=188.7 fps

I have seen no meaningful difference in readings if the microphone is placed a bit closer to one target than the other, but in any case the closer the microphone is to both, the more accurate the time, since the time it takes the sound to travel from the target to the microphone is added to the total time. If absolute speed is important, this effect can be calculated and corrected for.









Edited to correct failure to load of original image.


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## Hagencopen (Mar 4, 2011)

Thanks Henry ! This is very helpful indeed.


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## PandaMan (Oct 14, 2010)

Well? Were you successful? Wouldn't mind trying this myself.









P.S. does anyone know if it would work with air rifles? I really need to find out the speed.


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## Hagencopen (Mar 4, 2011)

PandaMan said:


> Well? Were you successful? Wouldn't mind trying this myself.
> 
> 
> 
> ...


 Yep. I am getting correct readings now ! Henry was right on, it was my method of measurement that was skewing my numbers. I simply set up 2 barriers(sheets of paper) a fixed distance from each other, then placed the mic about midway between. Shoot through, and record both impacts, and voila.

This would definately work for air rifles.


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## PandaMan (Oct 14, 2010)

Hagencopen said:


> Yep. I am getting correct readings now ! Henry was right on, it was my method of measurement that was skewing my numbers. I simply set up 2 barriers(sheets of paper) a fixed distance from each other, then placed the mic about midway between. Shoot through, and record both impacts, and voila.
> 
> This would definately work for air rifles.


Awesome. I will be using this method then.


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## Henry the Hermit (Jun 2, 2010)

Hagencopen said:


> Well? Were you successful? Wouldn't mind trying this myself.
> 
> 
> 
> ...


 Yep. I am getting correct readings now ! Henry was right on, it was my method of measurement that was skewing my numbers. I simply set up 2 barriers(sheets of paper) a fixed distance from each other, then placed the mic about midway between. Shoot through, and record both impacts, and voila.

This would definately work for air rifles.
[/quote]

Yep, but it almost certainly *won't* work for firearms.


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## PandaMan (Oct 14, 2010)

What kind of microphone can you use? I have headphones with a microphone on, could I use that? If not, are there any cheap but good microphones out there? (Cheap as in £5-10 ($8.14-14.28))


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## Henry the Hermit (Jun 2, 2010)

Just about any computer microphone will work. I just use the one built into my Acer Netbook.



PandaMan said:


> What kind of microphone can you use? I have headphones with a microphone on, could I use that? If not, are there any cheap but good microphones out there? (Cheap as in £5-10 ($8.14-14.28))


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