Effects of automotive microphone frequency response characteristics and noise conditions on speech and ASR quality -- an experimental evaluation
This study addresses the critical microphone selection problem for in-vehicle hands-free communication and automatic speech recognition (ASR) systems, focusing on the practical impact of frequency response characteristics—specifically bandwidth and amplitude-frequency curve—under realistic in-cabin noise conditions. Leveraging the ETSI TS 103 281 standard (S-MOS/N-MOS/G-MOS), signal-to-noise ratio (SNR), and word error rate (WER), we conduct a systematic evaluation using multi-source noise data collected from real vehicles. Our analysis quantifies, for the first time, the nonlinear effects of low-frequency cutoff, high-frequency upper limit, and mid-band gain profile on noise robustness and ASR accuracy. Based on these findings, we propose microphone frequency response optimization guidelines tailored to automotive environments. These guidelines provide empirically validated, reproducible evidence and actionable engineering insights for defining automotive-grade microphone specifications and guiding system-level acoustic design.