<p>Quantitative approaches in cultural heritage enable investigation of architectural features, which may be related to intangible functional knowledge. Medieval bell towers, derived from defensive watchtowers, have rarely been studied as acoustic devices shaping sound transmission. This study examines the 12^th century Norman bell tower of Salerno Cathedral (Italy) to determine whether its belfry cell operates as a resonant cavity compatible with the housed original 13^th century bell. Acoustic measurements and finite-element modelling show statistically significant spectral correspondence and position-dependent radiation enhancement, indicating the potential existence of an acoustic coupling and how to maximize it. These results provide quantitative evidence that implicit empirical knowledge of the time could support communicative acoustic functions, offering also a reproducible framework linking architectural form and intangible sonic heritage.</p>