Speaker
Description
This study investigates the measurement and evaluation of the Speech Transmission Index (STI) of emergency broadcasting speaker systems in noise barrier tunnels under emergency conditions such as fire incidents. STI measurements were conducted for two types of directional loudspeakers in both a semi-anechoic chamber and an actual noise barrier tunnel. The evaluation was conducted under various conditions, including speaker mounting height, speaker orientation, and the distance between the sound source and the receiver.In addition to STI evaluation, sound pressure levels (SPL) were measured and analyzed under each test condition. STI measurements were performed using two methods: a pink noise signal radiated from the loudspeakers and a speech-based method utilizing a talk box. The SPL results confirmed that the target sound pressure level of 80 dB or higher was achieved under the tested conditions. Furthermore, the STI evaluation results demonstrated that the target STI value of 0.60 or higher was successfully satisfied. [ This work was supported by the Technology Innovation Program [(RS-2025-05492970, Development of a Disaster-Responsive Noise Barrier System for Ensuring Evacuation Safety in Tunnel Fires) funded By the Ministry of Interior and Safety)(MOIS, Korea)]