Reference-free SNR Measurement for Narrowband and Wideband Speech Signals in Car Noise

Signal-to-noise (SNR) measurement of noisy speech signals is an important topic, e. g., in automotive environments. This paper presents an approach which aims to measure the SNR of a speech signal distorted by stationary noise as close as possible to a reference-based SNR measurement according to the ITU-T Recommendation P.56, however, without using any reference signals. The proposal offers low computational complexity, and it can be applied to narrowband and wideband signals within a typical SNR range. The measured SNR is calculated by means of a separate estimate of speech and noise power, resulting in raw SNR measurements which have to be corrected by a mapping function. The proposal was evaluated thoroughly by means of speech data in 15 different languages and car noise data. The proposed method achieves a correlation coefficient larger than 0.99 compared to state-of-theart reference-based SNR measurement employing P.56 reference levels of speech and noise. The method is proposed for a new ITU-T Recommendation within Study Group 12, Focus Group Carcom.