An important factor for the life quality in urban centres is related to the noise levels to which the population is submitted. Several factors interfere with the amount of noise pollution throughout the city. Among them, and as one of the most important, is the traffic noise. A major challenge is the quantification of the noise effects on the population. Not only high levels must be assessed but also the amount of people exposed to them is of great importance. This task is far from obvious since the sound propagation is affected by many environmental characteristics distinct in nature. The topology of the buildings and the topography may create quiet zones even in crowded neighbourhoods. Traffic may statistically vary. The population exposed might be resident but also fluctuate, not to mention the subjective nature of the sound perception itself. In order to aid the urban planner cope with these difficulties, this chapter will comprehensively presents alternatives ranging from numerical simulation, called noise mapping, to measurement based noise monitoring. Noise mapping techniques together with standards for the calculation of noise propagation are powerful tools to aid urban planners in correctly applying noise abatement measures in an economically feasible way. Nevertheless the results of such mappings rely on a great amount of data, location and strength of noise sources, ground geometry, location and geometry of buildings, etc. This work also discusses the sensitivity of the obtained simulated noise levels to the quality and precision of the geometric data available. Actual measurements are however needed not only to verify the model assumed for the simulation but also for the noise pollution assessment itself. This can be achieved through local measurements of short duration or through long term monitoring in fixed places. The measurement techniques and procedures are addressed together with the creation of databases to help the decision making process of the urban planner