Signal-to-Noise RatioSNR
Definition
The ratio of desired signal power to background noise power, typically expressed in decibels.
Signal-to-noise ratio quantifies how much louder the speech signal is compared to background noise. An SNR of 20dB means the speech is 100 times more powerful than the noise — very clean audio. An SNR of 0dB means speech and noise are equally loud — challenging for ASR. Negative SNR means noise is louder than speech.
ASR accuracy degrades as SNR decreases. Most models perform well above 15dB SNR but struggle below 5dB. Data augmentation during training (adding noise at various SNRs) improves robustness. Good microphone placement, noise cancellation, and acoustic environment optimization help maintain high SNR in practice.