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Audacity audio from slingshot
Posted: Mon Aug 31, 2009 12:33 pm
by boyntonstu
Using a wireless mic to Audacity in my PC I got this audio of a marble shot.
The first blip is the firing, the second, the hit, and the third a ricochet.
It is not fast.
I wouldn't even call it half-fast. lol
I don't know why it was so slow traveling 20 feet.
BoyntonStu
Posted: Mon Aug 31, 2009 3:45 pm
by jimmy101
Kind of hard to read the times from the image (and the link doesn't work).
Is that 0.26 seconds for 20 feet (77 ft/sec)? You can probably throw a marble faster than that.
Posted: Mon Aug 31, 2009 3:46 pm
by POLAND_SPUD
first of all, it's a slingshot... how can you precisely tell when it left the 'muzzle'
? (I don't really know what produces sound when you fire a slingshot)
it might be a better idea to use a camera and watch it in slowmo using some video editing software... even windows movie maker would be ok for this application
secondly, you have to take into consideration the speed of sound... that is how much time sound travels from your target to the mic
Posted: Mon Aug 31, 2009 4:06 pm
by boyntonstu
POLAND_SPUD wrote:first of all, it's a slingshot... how can you precisely tell when it left the 'muzzle'
? (I don't really know what produces sound when you fire a slingshot)
it might be a better idea to use a camera and watch it in slowmo using some video editing software... even windows movie maker would be ok for this application
secondly, you have to take into consideration the speed of sound... that is how much time sound travels from your target to the mic
Correct, except when the mic is midways between the muzzle and the target.
The SOS delay is the same for both paths.
Look at the little squiggle to the left of the first pip.
I believe that it is the sound of rubber relaxing.
Thanks,
BoyntonStu
Posted: Mon Aug 31, 2009 4:37 pm
by POLAND_SPUD
yeah but since you set it up right and you think that it was faster than 70ft/s then it might be exactly what I wrote in my first paragraph...
if I were you I would use a cam just to be sure... and to film some awesome damage vids at the same time
Posted: Mon Aug 31, 2009 4:38 pm
by Technician1002
Edited trace for easier viewing.
Request, could you save the sound as a mp3 and save it as a zip file? I would like to expand the relevant portions and listen to them to verify impact and launch noises. Audacity has the ability to zoom into portions to get high resolution on the timeline for launch and impact.
Posted: Mon Aug 31, 2009 4:39 pm
by JoergS
Stu, my experiments come to the same conclusion. You loose a lot of power when any mechanism is added to a slingshot. Friction, additional weight, such things play an important role.
You have to use a lot of rubber to compensate. Just two strings of Thera silver won't be enough. Go up on the rubber.
Posted: Mon Aug 31, 2009 6:57 pm
by boyntonstu
Technician1002 wrote:Edited trace for easier viewing.
Request, could you save the sound as a mp3 and save it as a zip file? I would like to expand the relevant portions and listen to them to verify impact and launch noises. Audacity has the ability to zoom into portions to get high resolution on the timeline for launch and impact.
I have the sound saved as a .wav file.
How can I send it to you?
BoyntonStu
Posted: Mon Aug 31, 2009 7:11 pm
by boyntonstu
JoergS wrote:Stu, my experiments come to the same conclusion. You loose a lot of power when any mechanism is added to a slingshot. Friction, additional weight, such things play an important role.
You have to use a lot of rubber to compensate. Just two strings of Thera silver won't be enough. Go up on the rubber.
Joerg,
Thanks, but I don't understand.
The gun pulls the rubber to the front fork.
My guess is that the mechanism beyond the rubber and the fork does not reduce the velocity.
The Nylon stretches and therefore it is pulling the rubber to beyond the front fork.
After a shot, the tubes are located below entering the pulleys.
They were pulled to that position with some force.
Is it possible that the nylon is buffering and slowing the rubber?
Perhaps I can lock the string and see the results.
The silver is stretched to 300+%.
I can pull against a 0-50 lb fish scale and measure the force.
I have no idea of why it is 5x slower than expected.
Even with the disappointing results, the project is quite challenging and fun learning experience.
BoyntonStu
Posted: Mon Aug 31, 2009 7:30 pm
by Technician1002
boyntonstu wrote:Technician1002 wrote:Edited trace for easier viewing.
Request, could you save the sound as a mp3 and save it as a zip file? I would like to expand the relevant portions and listen to them to verify impact and launch noises. Audacity has the ability to zoom into portions to get high resolution on the timeline for launch and impact.
I have the sound saved as a .wav file.
How can I send it to you?
BoyntonStu
Simply put it in a zip file, and attach the file. That way everyone can examine it. There are size limits to attachments so you may wish to convert to mp3 and then zip it.
Below is a short sample mp3 saved in a zip file of a couple cannons of mine.
Attach the file the same way a photo is attached.
Size can be reduced by converting a stereo track to mono, cropping the un needed parts and saving to MP3.
Posted: Mon Aug 31, 2009 7:43 pm
by boyntonstu
Technician1002 wrote:boyntonstu wrote:Technician1002 wrote:Edited trace for easier viewing.
Request, could you save the sound as a mp3 and save it as a zip file? I would like to expand the relevant portions and listen to them to verify impact and launch noises. Audacity has the ability to zoom into portions to get high resolution on the timeline for launch and impact.
I have the sound saved as a .wav file.
How can I send it to you?
BoyntonStu
Simply put it in a zip file, and attach the file. That way everyone can examine it. There are size limits to attachments so you may wish to convert to mp3 and then zip it.
Below is a short sample mp3 saved in a zip file of a piston cannon of mine.
Attach the file the same way a photo is attached.
Posted: Mon Aug 31, 2009 7:44 pm
by Mr.Sandman
Maybe you are hearing the bands snap back? I dont think that youll hear the ammo leaving the pouch. What slingshot is this btw?
Posted: Mon Aug 31, 2009 7:47 pm
by boyntonstu
Mr.Sandman wrote:Maybe you are hearing the bands snap back? I dont think that youll hear the ammo leaving the pouch. What slingshot is this btw?
I am not sure about the sound but it seems that the first large blip is the snap release.
Posted: Mon Aug 31, 2009 7:49 pm
by Mr.Sandman
Oh that slingshot.Haha I also have that pellet gun.Very good for my first. I now have a benjamin discovery. Hmm how close is the projectile to the mic when firing?
Posted: Mon Aug 31, 2009 7:59 pm
by boyntonstu
Mr.Sandman wrote:Oh that slingshot.Haha I also have that pellet gun.Very good for my first. I now have a benjamin discovery. Hmm how close is the projectile to the mic when firing?
The mic is on the floor at the 10 foot mark exactly between the target and the 'muzzle' of the slingshot.
The time delays are equal and are ignored.
BoyntonStu