In addition to the regulations in force, there often are standards defining a somewhat higher acoustic quality. Such standards are meant to acknowledge the efforts made to produce a better-than-average building (and eventually justify a higher rent too!).
For example, in France there used to be the Qualitel  standard, which typically aimed for acoustic objectives better than the regulations by 3 dB. In addition, it also introduced some basic requirements regarding sound insulation between rooms of a same dwelling.
In some countries there may be a standard defining what the normal behavior of the occupant of a dwelling is supposed to be; for example, in France there is a national standard  titled Normal Use Conditions of a Dwelling stating that the noise levels in terms of LAeq should not exceed 65 dB(A) in a dwelling. The same standard also points out that people are required to put their slippers on and avoid undue activity noise.