Sine wave noise at different frequencies

[sophiecentaur]

looking for signal under the noise floor.

So far, despite having posted a number of screen shots, you haven't yet said what you mean by noise floor.

I can't tell them I'm scanning the dark sector.

What does that mean in grown up language?

 

[berkeman]

Yeah, what's a dark sector?

I can't ask in the digital signal processing forums directly because I can't tell them I'm scanning the dark sector.

 

[sophiecentaur]

I was beginning to wonder about Ephant. I was thinking tinfoil hats etc..

 

[Ephant]

So far, despite having posted a number of screen shots, you haven't yet said what you mean by noise floor.

In Audacity, I was taught days after this thread was started that I could add noises in Audacity and see how they mixed up. So I was able to visualize the earlier question why 50Hz has more jagged edge vs 900Hz. .

This is 50Hz signal with 1000Hz noise.

This is 900Hz signal with 1000Hz noise.

Before I used the 1000 Hz software low pass filter in Audacity on the following 30,000 Hz signal. I didn't know what would happen. I thought if you didn't put any low pass filter on the hardware itself (like a 2nd order Butterworth filter). The noises would overwhelm the lower frequency increasing its noise. After I ran it. It became clear to me what it means the frequency spectrum of white noise is flat. And how white noise is characterized by a flat spectrum, i.e. the variance is approximately the same at all frequencies. And it is retained even after passing via an ADC. That's why you can do digital filtering like brick wall

And with your descriptions in the following. How can I not understand Noise Floor already. Of course Noise Floor doesn't mean there is a floor at the circuit where noise collects. It's like Sky is the Ceiling. There is no actual ceiling.

"The Noise we are discussing is a totally random fluctuation of a signal. Forget the sine wave ideas - that's just Maths and comes later. There is nothing in a hot resistor (or a transistor etc.) that consists of a sine wave oscillator there's just random fluctuations of charge carriers in there. When you look at a signal on a wire with an oscilloscope you will see a fuzz around the wanted signal that fuzz / grass is at a level that depends on the bandwidth that's been admitted by the input filter. "

What does that mean in grown up language?

In grown up language. It means ordinarily, dark matter (we who tried to detect it call it the dark sector) shouldn't interact with ordinary matter, even down to the photons. But the Big Bang should logically produce some kind of relics that can bind them together, sort of a coupler (restoring higher symmetry state lower than the electroweak plasma). In the past. They tried to find equations that could produce all the constants of nature, but couldn't. So the universe is more complicated than simple minded idea of it. And the idea is just slowing coming around the corner, and CERN is still transitioning to the idea the universe is more complicated than their rigid ideas as Sabine Hossenfelder kept saying.

Some of us believe ordinary and dark matter can be glued together. And we tried to detect it. No harm trying to detect it too for us civilians. But remember CERN are also composed of Civilians too, and very human.

 

[Ephant]

Oh. I couldn't edit the above message anymore. In the attachments I forgot to delete. The 3rd image is the white noise not yet filtered to 1000Hz, so it is still causing jagged edge even to 900Hz signal. Also the noise amplitude is just 0.3 while the sine wave is 0.8.

The noise and sine amplitude should be the same in the simulation, isn't it? The maximum is 1.0 but I used 0.8 to show the baseline better. I should have used 1.0 maximum amplitude white noise in the noise generator?

In the following I used 0.8 Noise with half right filtered to 1000Hz noise and a 50Hz signal

In the following I used 0.8 amplitude Noise with half right filtered to 1000Hz noise and a 900Hz signal.

Why do I share them? because it was when I saw them that I totally understand and visualize the reasons for jagged edges. You can let newbies try the Audacity noise generators who may not understand too.

About probing the noise floor using FFT. It is possible that many who didn't intend to probe the noise floor and using FFT just to view the signal above noise floor can unintentionally get signal from below the noise floor, is this right?

I need to know because if you show signals you acquired and didn't say some signal was below the noise floor. People who want to duplicate your result may only focus above the noise floor.

Also what would happen if you don't use FFT but just use Power Spectral Density analysis on the noises. Would you also be able to probe below the noise floor using PSD? This is my last question.

About my experiments to duplicate one done by a university. If I can't replicate it and it is faulty. Then the prospect of Particle Dessert for the next centuries is a possibility. But if I can replicate it. I'll share far and wide the findings of the University and all resources of CERN must be re-orient to the discovery instead of no major discoveries besides the Higgs. I'll update on the result months from now if I'm still here. I can't share the source now because it is not peer reviewed and may attract the wrath of the moderators. If I found sigma 5 results. I'll try to write or make other write a paper that can be peer reviewed and share here.

 

[sophiecentaur]

People who want to duplicate your result may only focus above the noise floor.

What exactly do you mean by this?

About my experiments to duplicate one done by a university.

What form do your experiments take? Is there any hardware or is it all on a simulator (which someone else wrote)?

CERN must be re-orient to the discovery instead of no major discoveries besides the Higgs.

So that's all they've achieved? They must be glad that you are around to put them on the right lines.

 

[Ephant]

What exactly do you mean by this?

I mean supposed a team used one hour sampling, and you use only 1 minute sampling and didn't know they used one hour to probe below the noise floor. Then you can't get the same data they have. I think this answers to my own question.

What form do your experiments take? Is there any hardware or is it all on a simulator (which someone else wrote)?

I'm just duplicating the experiment using room size Faraday cage (not yet built), very sensitive sensors and amplifiers, Matcad FFT/PSD/Paralac analysis etc.

So that's all they've achieved? They must be glad that you are around to put them on the right lines.

I mean the Large Hadron Collider major discovery was only the HIggs. Of course other accelerators/equipments before that confirmed the Standard Model like quarks, electroweak and others.

Since I'm getting some idea of the difference between FFT and Power Spectral Density. I googled a lot with some sites saying the spectrum looks the same, only the label varies, with the latter in W/Hz or other units. And will ask more in PSE, then I'll end up this thead with the following.

I think it may be more pessismistic to show them. 'll tell you why.
[Mentor Note: Several paragraphs of mystic nonsense deleted from this post]


Thank you guys for all the help. I have no futher questions about the subjects of this thread.

 

[berkeman]

I have no futher questions about the subjects of this thread.

Thread is closed then.