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Posted: Fri Oct 23, 2009 12:48 pm
by boyntonstu
bump: Hoping for analysis of the last .wav file.
Posted: Fri Oct 23, 2009 2:17 pm
by Technician1002
boyntonstu wrote:bump: Hoping for analysis of the last .wav file.
Wow, 3 downloads and no comments on the file.
Before the trigger there is a low frequency sound which the trigger event (hiss) rides on. The trigger starts at 0.130. At 0.150 there is a sudden increase in the hum, indicating the original valve vibration is back, but it lasts a cycle and a half with a valve burp at0 01670 seconds followed by one at 0.1690. I call these burps as the amplitude is way too quiet. The valve is still trying to open but the o rings appear to be sticking so it re-seats as some chamber pressure drops.
We finally get a full amplitude pressure swing that oscillates into a clipped square wave beginning at 0.730. Again the record level is way too high so the impact is showing up only as a change in the frequency of the noise. This change appears at 0.230 for a possible flight time of 0.500 seconds. It is really hard to be sure on this one. Is there a way to turn down the record volume a lot? The waveform clipping is making this difficult. A square wave is difficult to detect volume peaks due to an impact.
I will give credit to those who tried. It's not an easy waveform to measure.
Posted: Fri Oct 23, 2009 4:35 pm
by boyntonstu
Technician1002 wrote:boyntonstu wrote:bump: Hoping for analysis of the last .wav file.
Wow, 3 downloads and no comments on the file.
Before the trigger there is a low frequency sound which the trigger event (hiss) rides on. The trigger starts at 0.130. At 0.150 there is a sudden increase in the hum, indicating the original valve vibration is back, but it lasts a cycle and a half with a valve burp at0 01670 seconds followed by one at 0.1690. I call these burps as the amplitude is way too quiet. The valve is still trying to open but the o rings appear to be sticking so it re-seats as some chamber pressure drops.
We finally get a full amplitude pressure swing that oscillates into a clipped square wave beginning at 0.730. Again the record level is way too high so the impact is showing up only as a change in the frequency of the noise. This change appears at 0.230 for a possible flight time of 0.500 seconds. It is really hard to be sure on this one. Is there a way to turn down the record volume a lot? The waveform clipping is making this difficult. A square wave is difficult to detect volume peaks due to an impact.
I will give credit to those who tried. It's not an easy waveform to measure.
First, thank you.
Sorry about the clipping.
I am almost positive that the valve vibration is due to slow opening of the valve.
However, this shot was VERY powerful nevertheless.
Not only did the marble make a hole an go through the 5/8 plywood, it went about halfway into a 3/8 plywood sheet located behind the 5/8.
I will quiet down the mic some more and make an unclipped .wav.
BoyntonStu