The ASVspoof 2017 challenge is about the detection of replayed speech from human speech. The proposed system makes use of the fact that when the speech signals are replayed, they pass through multiple channels as opposed to original recordings. This channel information is typically embedded in low signal to noise ratio regions. A speech signal processing method with high spectro-temporal resolution is required to extract robust features from such regions. The single frequency filtering (SFF) is one such technique, which we propose to use for replay attack detection. While SFF based feature representation was used at front-end, Gaussian mixture model and bi-directional long short-term memory models are investigated at the backend as classifiers. The experimental results on ASVspoof 2017 dataset reveal that, SFF based representation is very effective in detecting replay attacks. The score level fusion of back end classifiers further improved the performance of the system which indicates that both classifiers capture complimentary information.
Automatic speaker verification systems are vulnerable to spoofing attacks. Recently, various countermeasures have been developed for detecting high technology attacks such as speech synthesis and voice conversion. However, there is a wide gap in dealing with replay attacks. In this paper, we propose a new feature for replay attack detection based on single frequency filtering (SFF), which provides high temporal and spectral resolution at each instant. Single frequency filtering cepstral coefficients (SFFCC) with Gaussian mixture model classifier are used for the experimentation on the standard BTAS-2016 corpus. The previously reported best result, which is based on constant Q cepstral coefficients (CQCC) achieved a half total error rate of 0.67 % on this data-set. Our proposed method outperforms the state of the art (CQCC) with a half total error rate of 0.0002 %.
In this paper, we propose to use hidden state vector obtained from recurrent neural network (RNN) as a context vector representation for deep neural network (DNN) based statistical parametric speech synthesis. While in a typical DNN based system, there is a hierarchy of text features from phone level to utterance level, they are usually in 1-hot-k encoded representation. Our hypothesis is that, supplementing the conventional text features with a continuous frame-level acoustically guided representation would improve the acoustic modeling. The hidden state from an RNN trained to predict acoustic features is used as the additional contextual information. A dataset consisting of 2 Indian languages (Telugu and Hindi) from Blizzard challenge 2015 was used in our experiments. Both the subjective listening tests and the objective scores indicate that the proposed approach performs significantly better than the baseline DNN system.
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