The categorisation method for the study of urban noise has been used with good results in cities with populations of between 50,000 and 330,000 inhabitants. However, its application in smaller towns has not been previously demonstrated. Thus, this work studies the impact of urban noise pollution in two towns of approximately 9,000 inhabitants, Olivenza (Spain) and Campo Maior (Portugal). The categorisation method was compared with the grid method. In addition, three methods for estimating the population affected by different noise levels were tested. The statistical analyses results showed that the categorisation method was applicable for small cities (of the studied size). In addition, the categorisation method was more suitable for the analysis of noise annoyance than the grid method. Conversely, because little information is available regarding the environmental problem of noise pollution in small towns, the noise exposures and the percentages of the populations annoyed by noise were compared with previous results from much larger towns.