The National Institute for Public Health and the Environment (RIVM) has examined the relationship between aircraft noise and severe annoyance or sleep disturbance for 14 airports in the Netherlands. This is referred to as the ER relationship. For most airports, the pattern is clear: the likelihood of severe annoyance or sleep disturbance increases as noise levels rise. However, the relationship can differ from one airport to another and may change over time. RIVM therefore advises policymakers to always use current, airport specific ER relationships. This will ensure the highest level of health protection from aircraft noise for people living near airports.