Image Noise
The Vivitek exhibits more image noise in it's best Movie mode, than many other projectors, but the same can be said of almost all DLP models. They just seem to produce a noisier looking image than LCD or LCoS projectors. It's there, but another non-issue for most.
When you switch to Bright mode, however, where there seems to be some dynamic enhancement going on somewhere, the image noise seems to mix with the higher dynamic, and on occasion the noise is noticeable and a touch distracting.
That's OK, though, as you are probably using Bright mode, primarily for sports type viewing where you aren't likely to notice, and less likely to care. That said, I have three images here, that show the Vivitek H1080FD projector on the same scene, but with the three different modes.
Look particularly at the noise in the woman's face, and especially the neck. In Movie mode, it just appears as a touch of noise as with any projector, Normal is a little worse but shouldn't be an issue. Bright mode, however, was starting to get visible at close, but normal seating distances. Again, though, Bright, as with any projector, is an inherent compromise between lumens and image quality.
Another note: In comparing these images above, you can see that the Vivitek does have a bit too much green in Bright mode (again, as is very typical). Besides noting the differences in color, I did want to say that the shift to green is there, but less noticeable on the screen, than in the picture. (I've commented many times that there is usually a little too strong green coming out of my dSLR when doing these shoots, that I've never been able to fully remove.)
Audible Noise
I complained about the audible noise of the Optoma HD20, when I reviewed it recently. OK, DLP projectors tend to be the noisiest of the three projector technologies, and it tends to be made worse when the manufacturers are building particularly small projectors like the HD20.
Fortunately, the Vivitek H1080FD is definitely quieter than the HD20. It's not night and day, but definitely several db worth. Vivitek claims 26 db in low power, which likely translates into 30 - 31 db at full power. And yest, that would be definitely quieter than the HD20, and about average among the lower cost DLP projectors.
The HD20 does appear to be noiser than some of the more expensive competition. It's likely just a little noisier than both the Mitsubishi HC3800 or the Epson Home Cinema 8100, two under $1500 projectors we really liked when reviewed.