Bandwidth extension for speech acquired by laser Doppler vibrometer with an auxiliary microphone

This paper proposes to extend the bandwidth of speech acquired by a system combining laser Doppler vibrometer (LDV) and an auxiliary microphone in adverse environments, where this system is referred to as LDV-AM. Traditional bandwidth extension (BWE) algorithms often need two stages to estimate the broadband spectral envelope. In the first stage, the codebook of the broadband spectral envelope is trained by a training data set. In the second stage, the broadband spectral envelope is estimated with the codebook by using different algorithms, such as neural networks and linear mapping. After considering that speech acquired by LDV only contains speech components lower than 2kHz, it seems improper to use the traditional BWE algorithms directly. Because these traditional BWE algorithms are often designed to extend narrowband telephone speech, which is sampled at 8kHz. With the help of the auxiliary microphone, the broadband spectral envelope of speech acquired by LDV can be estimated directly from speech acquired by this microphone. Experimental results show that the proposed BWE algorithm for LDV-AM can greatly improve MOS scores in adverse environments.