This study presents a use-case of a network of low-cost acoustic smart sensors deployed in the city of Pamplona to analyse changes in the urban soundscape during the San Fermin Festival. The sensors were installed in different areas of the city before, during, and after the event, capturing continuous acoustic data. Our analysis reveals a significant transformation in the city's sonic environment during the festive period: overall sound pressure levels increase significantly, soundscape patterns change, and the acoustic landscape becomes dominated by sounds associated with human activity. These findings highlight the potential of distributed smart acoustic monitoring systems to characterize the temporal dynamics of urban soundscapes and underscore how the large-scale event of San Fermin drastically reshapes the overall acoustic dynamics of the city of Pamplona. Additionally, to complement the objective measurements, a curated collection of real San Fermin sound recordings has been created and made publicly available, preserving the festival's unique sonic heritage.