The Belgian standards which are generally used in acoustics of the building are:

• NBN S 01-400: 1977 Acoustics - Criteria of sound insulation for residential buildings, since 19 May 2008, this standard is replaced by the new standard:
  NBN S 01-400-1: 2008 Acoustics - Acoustic Criteria  for buildings
  
• NBN 01-401 S: 1976 Acoustics - Limits of noise in Building

To access the BBRI standardization page click here.