Tenants in Viennese apartment buildings are generally very quiet and they are also very keen on this remaining so..
Legally it is not allowed to make any loud noises like loud talking, laughing, loud tv watching or music or (horrible word coming, don't read if you are overly sensitive)...partying (yuck!) after 10pm (22h) and until 6am.
Importantly, noise made by small children or babies crying are not legally considered as noise, so no worries if you have a small baby or a pair of very active small children.. the latter should be in bed at 10pm anyway.
So if you are a visitor in Vienna and want to know the etiquette, here you have it: keep noise levels low and enjoy the peaceful atmosphere while living in Vienna :-)