Traffic noise in cities has serious effects on the inhabitants. Well-known effects are annoyance and sleep disturbance, but long-term health effects such as cardiovascular disease have also been related to traffic noise. The spatial distribution of traffic noise in a city is related to the distributions of traffic volume and urban density, and also to urban form. This relation is investigated by means of numerical calculations for two cities, Amsterdam and Rotterdam, and for various idealized urban fabrics. The concept of urban traffic elasticity is introduced to relate local population density to local vehicle kilometers driven on the urban road network. The concept of Spacematrix is used to represent urban density and urban form. For the two cities it is found that the average sound level in an urban area decreases with increasing population and building density. The results for idealized urban fabrics show that the shape of buildings blocks has a large effect on the sound level at the least-exposed façade (quiet façade) of a building, and a smaller effect on the sound level at the most-exposed façade. Sound levels at quiet facades are in general lower for closed building blocks than for open blocks such as strips. © 2012 Elsevier B.V.