This paper brings the lessons of critical thinking of environmental indicators to transport studies. To demonstrate the extent to which these indicators are not neutral, the case study focuses on airport noise indicators imposed by both the European Union and Flanders, Belgium, as they are applied to Brussels Airport’s operations. Three directions have been considered. First, we unveil the spatial mismatch between protests and official noise contours that are supposed to reflect overall annoyance and sleep disturbance. Then we highlight the high sensitivity of the mandatory noise indicators (Lden, Lnight and dose-effect function) to both their definition and the thresholds considered. Second, we review the legislative process at the time the EU and Flanders adopted their regulation on noise assessment. It appears both the nature of the indicators and thresholds have been the subject of debate by EU Ministers and MPs, while Flanders has imposed a dose-effect function that is arguably outdated and unusable in specific cases. Finally, we discuss the results through the lens of the authoritative power of official noise indicators and related maps, which many journalists and scholars take for granted. All this contributes to the construction of distorted knowledge of noise issues and calls for a re-evaluation of the EU’s and Flanders’ noise indicators.