Jn,
Short bursts mathematically consist of continuous sines too. The shorter-duration and more steep-edged/abrupt the burst, the higher the frequency of some of the sines.
Short bursts mathematically consist of continuous sines too. The shorter-duration and more steep-edged/abrupt the burst, the higher the frequency of some of the sines.
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Post 34414. Note that the blue input signal and the green output signal are different frequencies.
My post 34595 shows that in better detail, as I used PSP*processing to do what I had asked him to do.
*Paper Scissor Processing
Luckily, I did not cut or stab myself with the scissors, but running was not involved..
I did not scan the composite when I calculated the 17.5khz frequency of the green output. Each time mark is 60 uSec, I divided one into 6 semi equal segments, three cycles of the green were 170 uSec total.
Jn
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Have a very close look at that animation I posted and you might see what's actually happening in the time domain and why it's not particularly useful when it comes to "seeing" the frequency
Can't tell if you're being deliberately obtuse or are making a (pretty funny, actually) joke, kinda Groucho Marx. You Europeans speak too many languages for your own good. Harumpf!
But the question remains: what is the source of this modulation, and why can't it be measured with ordinary conventional means? If you see it in a model, but not in the real world, how good is the model?
Much thanks, as always,
Chris
Which has been precisely my point.
Jn
Scottjoplin, while the animation is really cool, it is not useful for our discussion, and as you say, not particularly useful when it comes to seeing the frequency. Look at the post numbers I provided. Perhaps you can explain the output frequency of 17.5 kHz where a 20 kHz signal was put in?
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In any other context, when you see something in a model that's never seen in the real world, which do you suspect of error?
Much thanks, as always,
Chris
If you recall (which you obviously don't), I requested others try the exact same test to confirm the results as repeatable.
Also, if you recall (again you don't), Han's provided an input and output which obviously were two different frequencies and said "there is nothing obviously different here".
To me, a frequency shift from 20 kHz to 17.5 kHz requires an explanation. Are you saying his model is wrong?
Honestly, everybody is so caught up in the digital processing/frequency domain, they are frightened to try to look in the time domain.
Jn
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T:
You should try living here. On second thought, maybe not. Too much here here.
Always the best fortune,
Chris
You should try living here. On second thought, maybe not. Too much here here.
Always the best fortune,
Chris
Here's his original quote:
I consider the frequency shift alarming, but that's just me..
Hey, you have to give the guy a break, it wasn't that obvious at first glance.
Jn
I consider the frequency shift alarming, but that's just me..
Hey, you have to give the guy a break, it wasn't that obvious at first glance.
Jn
I'm not sure of the exact definition, but I'm pretty sure you would know, could that be described as a strawman argument?
I'm not sure. I have to think about that. Did I refute a construct that was not made?
Perhaps instead of frightened, maybe unaccustomed to using, or too comfortable with frequency domain to look at time domain? Not sure how to best put it.
Jn
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Not really. Take your phantom 20kHz signal from before. The frequency of a cyclic signal is the inverse of the period it takes the pattern to repeat (the whole pattern, not just an eyeballed part of it). The repeating pattern itself doesn't recur at a 20kHz rate, does it? So why do you want to see/call it as 20kHz?
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I'm not sure, is that like a double negative? Just seen your edit, carry on, keep digging, I think you'll get there, constructing something that isn't there/wasn't said etc... 😉
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I have no idea what you are trying to say.
I added two sines mathematically, it shows a beat, and the frequency within the modulation envelope was the mathematical average of the two , sign flipped every envelope. Oddly enough, a 20 kHz sine tracks the carrier exactly.
Trig identity:
Sin(a) + sin(b) = 2(sin ((a+b)/2)cos((a-b)/2))
Sin(17.5) + sin(22.5) =2sin(20)cos(2.5)
So, there's the 20, seventh grade trigonometry. Honestly, I had to look it up..😱
Jn
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Well that really added to the technical content.
I do find it odd that nobody else has duplicated Han's effort, don't you?
I mean, if it's incorrect due to error, wouldn't anybody want to know?
Jn
The only thing I find odd is that you don't appear to understand what people are saying. BTW did you listen to PMA's file, could you hear a 200Hz tone?
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