The influence of firefighting experience on speech-in-noise recognition with two-way radios

Clear communication is critical for firefighters' safety, but high noise levels, hearing loss, and protective equipment impair speech understanding. This study investigates the performance of two-way radios in noise and examines their effects on speech-in-noise recognition related to noise levels, hearing thresholds, and firefighting experience. We first characterized the acoustic performance of Motorola APX 7000xe radios using MATLAB. Speech recognition was then tested using the Quick-SIN with two listener groups (n = 12 firefighters; n = 20 non-firefighters). Target sentences, recorded with KEMAR simulators, were presented in quiet and fire noise at fixed SNRs (−9 and −15 dB), yielding four test conditions. Realistic fire noise was simulated using auditory steering to create a surround sound effect relative to the radio position. Listeners repeated sentences heard over headphones and were scored on correct keywords. Preliminary control group results show significant speech intelligibility decline with radio use, even in quiet. In noise, performance dropped further, with 59% correct at −9 dB SNR and 40% at −15 dB SNR. The radio system's bandpass filter prioritized speech frequencies (1700-3200 Hz) but still posed challenges. Data from 12 firefighters are currently being analyzed to assess how hearing thresholds and experience affect performance, guiding future communication strategies.