This document summarizes a study comparing noise exposure in European cities using the group noise exposure indicator Gden. The study finds Gden correlates well with annoyance levels when cities are grouped by noise curve shapes and mapping methods. It applies Gden to noise map data from across Europe, finding some national clusters. The study also compares Gden to the Qcity local hotspot identification method, finding Gden is faster but less detailed. Gden is concluded to be a useful high-level indicator for comparing noise levels between cities and tracking policy impacts over time.