A simplified audio crony

Discussion in 'General Slingshot Discussions' started by Arturo Borquez, Feb 7, 2013.

  1. Arturo Borquez

    Arturo Borquez Administrator

    3,609
    0
    0
    I've done some Audacity crony the 2 paper method but I find it <br>cumbersome ... my goal is only compare different setups ... <br><br>was <a href="http://www.youtube.com/watch?v=igENqEJw43M" class="postlink" target="_blank" rel="nofollow">THIS</a> video who gave me the clue, ammo separation occurs very near the fork tips, and found a persistent and consistent pattern in all the audio I have, a train of noise during acceleration (band retraction) a little pause and a second train of noise (empty bands and recoil, this can be seen here<br>[​IMG]<br>I am speculating that is what the IPhone and Ipad crony does, <br><br>so I did the<br> following calculus upon the pattern showed:<br><br>ammo separation: 0.064521 secs.<br><br>target hit: 0.156795 secs.<br><br>given I were standing at 7.8 meters (from the catch box base) and <br>target is 0.15 inside = 7.95 meters (for sound correction delay), that <br>means the sound took 7.95/330 = 0.024 secs delay from the target to the <br>mic ...<br><br>the net distance is 7.95 minus my arm length which is 0.5 meters, that gives 7.45 meters so:<br><br>target hit time - OTF time - sound correction = net time<br><br><br><br>0.156795 - 0.064521 - 0.024 = 0.068274 secs.<br><br><br><br>so the speed should be net distance / net time that gives:<br><br><br><br>7.45 / 0.068274 = 109.12 meters / second or 358 FPS.<br><br><br><br>what do you think guys, do my results make sound to you?, can be used for comparative purposes? ...
     
  2. onnod

    onnod Im from Holland, isnt that weird?

    6,001
    18
    38
    Hmmm, this had my brain for a couple of minutes, i think that... you did something i do not understand fully, hmm, i have to think some more but i think it makes sense.<br><br>More thinking is done and it makes sense
     

  3. FIAAO

    FIAAO Failureisalwaysanoption

    3,648
    19
    38
    I think it makes sense (too)!
     
  4. cobble

    cobble New Member

    3
    0
    0
    Just curious how you got so many significant figures on your numbers. Are you reading them of the graph? How did you get the graph? Is that an Iphone app? Thanks!<br>
     
  5. Arturo Borquez

    Arturo Borquez Administrator

    3,609
    0
    0
    <table width="90%" cellspacing="1" cellpadding="0" border="0" align="center">
    <tr><td><span class="genmed"><b>cobble wrote:</b></span></td></tr>
    <tr><td class="quote"> Just curious how you got so many significant figures on your numbers. Are you reading them of the graph? How did you get the graph? Is that an Iphone app? Thanks!<br>
    </td></tr>
    </table>
    <span class="postbody"><br>yes I get them from the graph this way :<br>[​IMG]<br>and were validated with the Chrono-Connect app for Android smartphones (my son's), but this app is for airgun rifle not made for slingshot so it deviates 5% from a true crony. The pattern for a slingshot is different because there are 2 peaks regions of noise (acceleration and entangling)<br>The audio record was obtained with soundconvert app from a recorded avi video and the pattern shown is valid for OTT setups with Audacity app<br><br>1 RELEASE<br>2 ACCERATION NOISE (Bands retracting)<br>3 AMMO SEPARATION (no more force bands are moving with the residual inertia, minimal noise)<br>4 ENTANGLING BAND NOISE<br>5 TARGET HIT<br><br>At point 3 (minimal noise) the ammo is one band length behind the fork tips, also you must take account for your arm length and the sound traveling delay, anyway it is less cumbersome than the 2 paper method setup. It gives the mean velocity, a real crony shows the instantaneous speed ...<br>Cheers<br>Arturo</span>
     
  6. Firelad

    Firelad New Member

    15
    0
    0
    Too complicated <img src="http://illiweb.com/fa/i/smiles/icon_eek.gif" alt="Shocked" longdesc="5">
     
  7. Arturo Borquez

    Arturo Borquez Administrator

    3,609
    0
    0
    Not so much, a few arithmetic operations and you are done, much more complicated is the 2 paper setup ...<br>SC=D/330 (recording from behind you)<br>T=T5-T3-SC<br>V=(D-AL+L)/T<br>where SC=sound speed delay correction<br>D=distance to the target<br>AL=arm length<br>L=bands length<br>and V is the mean speed in meters per second or whatever unit used ...<br>anyway a crony is better, but I don't need it, I can do relative performance comparisons with this method, more than enough for me ...<br>Cheers<br>Arturo