The sonic environment of the urban public space is often experienced while walking through it. Nevertheless, city dwellers are usually not actively listening to the environment when traversing the city. Therefore, sound events that are salient, i.e. stand out of the sonic environment, are the ones that trigger attention and contribute highly to the perception of the soundscape. In a previously reported audiovisual perception experiment, the pleasantness of a recorded urban sound walk was continuously evaluated by a group of participants. To detect salient events in the soundscape, a biologically-inspired computational model for auditory sensory saliency based on spectrotemporal modulations is proposed. Using the data from a sound walk, the present study validates the hypothesis that salient events detected by the model contribute to changes in soundscape rating and are therefore important when evaluating the urban soundscape. Finally, when using the data from an additional experiment without a strong visual component, the importance of auditory sensory saliency as a predictor for change in pleasantness assessment is found to be even more pronounced.