Characteristic of room acoustical parameters with source-receiver distance on platform in subway stations

Prior to proposing appropriate standard for subway station platform, this study conducted field measurements to examine characteristics of room acoustics on platform of two subway stations. As a result analyzing the longitudinal length of the platform, Sound Pressure Level (SPL) decreased (maximum difference : 14 dB), Reverberation Time (RT) tended to increase (maximum difference of 0.8 s similar to 1.5 s), and C50 and D50 were decreased (maximum difference: 5.9 dB similar to 9.1 dB and 31.8 % similar to 37.6 %, respectively) as measurement positions moved away from the sound source. The Interaural Cross-correlation Coefficient (IACC) did not show clear tendency, but it was lower than 0.3 in entire points. It is judged that the subway platform has non-uniform sound field characteristics due to various combinations of direct and reflective sound even though it is finished with a strong reflective material.This indicates that the room acoustic characteristics of the near and far sound field are clearly expressed depending on the source-receiver distances in the subway platform having a long flat shape with a low height compared to the length.Therefore, detailed architectural and electric acoustic design based the characteristics of each location of speaker and sound receiver in the platform is required for an acoustic design with clear sound information at all positions of the platform.