Sound field characteristics and influencing factors of traditional Chinese interlocked timber-arched covered bridges

As an important type of traditional architecture in China, Chinese interlocked timber-arched covered (CITAC) bridges provide transportation functions, while interior spaces are also utilized for ritual activities. The unique spatial form of the CITAC bridge considerably influences the internal sound field. In this study, field measurements and acoustic simulations were conducted to determine the sound field characteristics of CITAC bridges and analyze the influencing factors. The results indicate that the mid-frequency reverberation time (RT30M) of the four measured CITAC bridges ranged between 0.37 and 0.50 s. The spatial dimensions, enclosure structure systems, and occupancy of the CITAC bridges all influenced their sound fields: increasing the bridge length or adding gable walls on both sides significantly increased RT30M; as the opening angle of the protective wooden panels beneath the eaves increased by 15°, the mid-frequency early decay time (EDTM) inside the CITAC bridge decreased by approximately 10%. EDTM and RT30M were approximately 20% lower in the occupied condition than in the unoccupied condition. In addition to the cross-sectional aspect ratio, the influences of other spatial elements on the sound fields of CITAC bridges align with previous studies on the sound field characteristics of long spaces.