How would you deal with this tenant situation? (Strong Language)

[Ben Staples]

https://www.youtube.com/watch?v=N93hMTBPRbc (Warning, there is strong language in this video)

My friend recently showed me this video of a situation between two tenants in what looks like an apartment complex. One claims the upstairs neighbor has been stomping around, while the other claims the downstairs neighbor has been playing music too loud. I feel like this is a very common situation where people living in relatively close quarters don't mesh well and would like to hear your thoughts:

Situation 1: The upstairs neighbor (The one that recorded this video) comes to you to complain. What actions or next steps do you take after watching this video?

Situation 2: The upstairs neighbor comes to complain, but did not record the encounter. How would your actions or next steps change?

Lastly, are there materials you can use, or changes in the way you design floor plans to reduce neighbor noise in small multi families or apartment buildings?