Noise present in JPG that ISN'T see in LR!?

[Hersh23]

Hello! This is my first time posting here some hopefully I'm posting in the right spot and can get an answer. Recently I was shooting at a concert. Not the greatest of lighting so naturally I had to bump up the ISO on my camera and was expecting noise on my images. The issue I'm having is that once I have finished editing in Lightroom and Export, the JPG version of what I just exported seems to have a lot more visible noise compared to what I was looking at in Lightroom!

I have provided some comparison screenshots of this.

Here is a shot as seen in LR, finished and ready to be Exported:

Now here is the same image when I view it through Windows Photo Viewer as a JPG after I have Exported. There is a notable amount of noise in this one:

Here is a Zoomed In View of the image in Lightroom:

And a Zoomed In View of the same image after it has been Exported, as seen through Windows Photo Viewer, where for some reason there is a LOT of noise present when compared to how the image looks in LR:

So my question. What in the world is causing such a difference!? It's pretty disappointing to work on an image in LR, be satisfied with what I see, Export it only to see that after I have Exported it actually has a lot more noise than I intended and expected! Is there a setting within LR that I am overlooking?
Here is a screen shot of my Exporting settings. I believe everything should be ok? I tend to shoot a lot in daylight so low light concert photography is new-ish to me. This gig I shot didn't have the most amazing of lighting so Noise was expected but the difference in noise between what I see in LR and what I see post-Export is concerning:

I am using Windows 10 and a retail version of Lightroom 6, if that means anything. Hopefully I get an answer that will help me retain the image quality I see in LR!

[Per Berntsen]

To evaluate noise and sharpening, you have to view the image at 1:1 – any other view will be inaccurate and misleading because the image has been scaled. At 1:1, one image pixel is represented by one screen pixel, and this will give you a true representation of the image. For the same reason, you also have to apply noise reduction and sharpening at 1:1.

All this applies not only to Lightroom, but any application that you use to view images.

So you need to view at 1:1 (100%) in Photos as well, where it should match what you see in Lightroom at 1:1.

Different applications use different algorithms for scaling images, so there may not be match at other magnifications.

[Hersh23]

Wooooooooooooooooooowww...well I'll be damned! I mean, I've reduced Noise before in other photos and it's never been an issue, perhaps because the original image didn't have THAT much noise. But now I am comparing the image in LR 1:1 to the JPG of the same image 1:1 and they are identical. I had no idea that LR and perhaps other programs display images slightly different and when it comes to Noise reduction (ESPECIALLY in an image that originally has high noise), it's best to edit and view 1:1.

Looks like I still have some editing to do. Quite a bit of editing actually, but thank you for the answer!

[Per Berntsen]

I had no idea that LR and perhaps other programs display images slightly different and when it comes to Noise reduction

It's not only noise that's affected by scaling – sharpness, chromatic aberrations and moiré are also affected.

Scaling involves varying amounts of sharpening and smoothing, and it appears that the Photos app applies more sharpening than Lightroom.

Noisy images need to be sharpened carefully, so that the noise isn't amplified by sharpening.

Use the Masking slider to control what areas of the image that will be sharpened. Hold down the Alt key while dragging the slider, and you will see the effect. Black areas will be protected, and white areas will be sharpened.

A high Masking setting (70 - 90) will protect flat areas (where noise in most noticeable) from sharpening, whereas sharp edges will be sharpened. When Masking is set to 0, everything, including noise, will be sharpened.

This workflow can reduce the need for noise reduction, and I suggest that you sharpen the image first, and then apply noise reduction. All this of course has to be done at 1:1 view.