Greg, I read through the presentation poster a few times last night, and I hope you are open for a question or two. I am specifically interested in the sound/Audacity method. If I understand your set up correctly, you used one mic midway between the bow and the target? Then moved the target back some, and adjusted your equation for the second distance?
It doesn't matter where the mic is honestly. We did it that way because the shooting machine was noisy and had a hard time picking up the impact. However, if your shooting by hand or had a less noisy machine, It might be better to have the mic next to you or behind you. You want to be able to hear both the release and the impact. Like I said there is no right spot for the mic, you just have to measure the distance it is from the bow, and the distance it is from the target. If you move yourself or the target to shoot at a different distance you have to readjust the equation since those distances have changed. Did I include that equation on the poster? if not it can be found on pg 19 of this article
https://arxiv.org/ftp/arxiv/papers/1511/1511.02250.pdfSince the equation above only gives the velocity at the distance of the target, it would be slower due to drag.
Wouldn't the speed be the average speed between the bow and the target, rather than the speed at the target?
Thanks
You are correct. It would be the average speed. However, there is still a decay, the average speed at 30 yards is going to be less than the average speed at 20. So I fibbed a little bit when I said it was the instantaneous velocity at the distance of the target. Most people wouldn't pick up on the idea of the whole average things as easily, so I used instantaneous Velocity as an easier way of explaining it. Regardless it shouldn't affect your ability to find the instantaneous velocity at release since the average of 1 yard is going to be pretty much that.
Another note I feel I should mention is that it's important to get several different readings at different distances in order to get that decay rate (unless you just cared about average velocity instead of instantaneous velocity at release). We originally wanted to do 20 yards, 25 yards, and 30 yards, but had an issue with changing draw lengths in the indoor range, so we only ended up with two viable distances. I would still go with at least three and I feel you would get a better slope for decay rate. It's also important to not shoot so close. There was a problem we were encountering in this thread (
http://www.primitivearcher.com/smf/index.php/topic,59214.msg821468.html#msg821468) where if you are shooting at too short of distances you have to be so much more accurate with your measurements, that even the difference of the arrow sound coming from the end of the arrow on release but the impact sound coming from the tip of the arrow on impact, made a big difference. It made it so you had to alter the equation to account for that arrow length to get accurate results. Even then it still had issues. I have learned that you probably don't want to shoot at any distances closer than 20 yards. I even think 15 yards would be pushing it. At further distances, the arrow length should be a negligible factor.
