“What differentiates an exemplary digital signage installation from environmental noise?”
In my opinion, digital signage (like every other medium) needs to communicate the message to the viewer in an efficient and memorable way. If you are driving down the road and the billboard has eight lines of writing, no one wins. To give an example of good signage, there is a large soft drink company that features one product at a time and adds a very short tagline. That tells the viewer to See This, Drink This, Be Happy. It’s all about “eyeball time” combined with attention span. Environmental noise might look good in a boardroom, but just becomes a wasted check in the field.