Abstract
In this paper, a multi-task learning U-shaped neural network (MTU-Net) is proposed and applied to single-channel speech enhancement (SE). The proposed MTU-based SE method estimates an ideal binary mask (IBM) or an ideal ratio mask (IRM) by extending the decoding network of a conventional U-Net to simultaneously model the speech and noise spectra as the target. The effectiveness of the proposed SE method was evaluated under both matched and mismatched noise conditions between training and testing by measuring the perceptual evaluation of speech quality (PESQ) and short-time objective intelligibility (STOI). Consequently, the proposed SE method with IRM achieved a substantial improvement with higher average PESQ scores by 0.17, 0.52, and 0.40 than other state-of-the-art deep-learning-based methods, such as the deep recurrent neural network (DRNN), SE generative adversarial network (SEGAN), and conventional U-Net, respectively. In addition, the STOI scores of the proposed SE method are 0.07, 0.05, and 0.05 higher than those of the DRNN, SEGAN, and U-Net, respectively. Next, voice activity detection (VAD) is also proposed by using the IRM estimated by the proposed MTU-Net-based SE method, which is fundamentally an unsupervised method without any model training. Then, the performance of the proposed VAD method was compared with the performance of supervised learning-based methods using a deep neural network (DNN), a boosted DNN, and a long short-term memory (LSTM) network. Consequently, the proposed VAD methods show a slightly better performance than the three neural network-based methods under mismatched noise conditions.
Highlights
Speech enhancement (SE) has been widely used as a preprocessing step in speech-related tasks, such as automatic speech recognition, speaker recognition, hearing aids, and enhanced mobile communication
(k), speech signal is estimated by applying an such as: ideal ratio mask (IRM) is multiplied to the noisy input speech spectrum, which results in the estimation of the clean speech spectrum; the estimated clean speech in the time domain is reconstructed by applying an inverse FFT (IFFT) H (k)|Y (k)| exp j∠Y (k)
This section first evaluates the performance of the proposed multi-task learning U-shaped neural network (MTU-Net)-based SE method and compares it with those of several conventional SE methods based on sparse NMF (SNMF) [Error! Reference compares it with those of several conventional SE methods based on SNMF [3], SE generative adversarial network (SEGAN) [8], deep recurrent neural network (DRNN) [5], source not found.], SEGAN [Error! Reference source not found.], DRNN [Error! Reference source and U-Net [15]
Summary
Speech enhancement (SE) has been widely used as a preprocessing step in speech-related tasks, such as automatic speech recognition, speaker recognition, hearing aids, and enhanced mobile communication. Sci. 2020, 10, 3230 such as the deep denoising autoencoder [4], deep recurrent NN (DRNN) [5], and convolutional NN (CNN) [6] These methods provide a high signal-to-noise ratio (SNR) due to their good estimated magnitude spectrum matching to clean speech, but the intelligibility of the estimated clean speech is somewhat degraded when using the noisy input speech phase for clean speech estimation. A single-channel SE method is proposed based on a multi-task learning U-Net (MTU-Net) architecture to provide a better estimate of the IRM and to simultaneously perform VAD.
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