On the monodromy of the moduli space of Calabi-Yau threefolds coming from eight planes in P3\mathbb{P}^3

It is a fundamental problem in geometry to decide which moduli spaces of polarized algebraic varieties are embedded by their period maps as Zariski open subsets of locally Hermitian symmetric domains. In the present work we prove that the moduli space of Calabi-Yau threefolds coming from eight planes in $\mathbb{P}^3$ does {\em not} have this property. We show furthermore that the monodromy group of a good family is Zariski dense in the corresponding symplectic group. Moreover, we study a natural sublocus which we call hyperelliptic locus, over which the variation of Hodge structures is naturally isomorphic to wedge product of a variation of Hodge structures of weight one. It turns out the hyperelliptic locus does not extend to a Shimura subvariety of type III (Siegel space) within the moduli space. Besides general Hodge theory, representation theory and computational commutative algebra, one of the proofs depends on a new result on the tensor product decomposition of complex polarized variations of Hodge structures.Comment: 26 page

A general framework for incorporating time-frequency domain sparsity in multi-channel speech dereverberation

status: publishe

Combined single-microphone wiener and MVDR filtering based on speech interframe correlations and speech presence probability

For single-microphone noise reduction, a minimum variance distortionless response (MVDR) filter has been recently proposed based on speech correlations of consecutive time frames. This filter is able to keep speech distortion low but compared to conventional approaches achieves less noise reduction. Further, when only having access to the noisy speech, more artifacts in the background noise are audible due to estimation errors of the speech interframe correlations, especially in time-frequency regions where speech is not dominant. Therefore, in this paper we propose to apply the MVDR filter where speech is dominant and the singlechannel Wiener filter otherwise, using a weighting based on the speech presence probability. In addition, we modify the decision-directed approach to estimate the a priori SNR in a more robust way for short analysis frames. Experimental results show that the proposed scheme achieves a better speech quality compared to the MVDR filter and the single-channel Wiener filter

Constrained multi-channel linear prediction for adaptive speech dereverberation

status: publishe

Subjective speech quality and speech intelligibility evaluation of single-channel dereverberation algorithms

In this contribution, six different single-channel dereverberation algorithms are evaluated subjectively in terms of speech intelligibility and speech quality. In order to study the influence of the dereverberation algorithms on speech intelligibility, speech reception thresholds in noise were measured for different reverberation times. The quality ratings were obtained following the ITU-T P.835 recommendations (with slight changes for adaptation to the problem of dereverberation) and included assessment of the attributes: reverberant, colored, distorted, and overall quality. Most of the algorithms improved speech intelligibility for short as well as long reverberation times compared to the reverberant condition. The best performance in terms of speech intelligibility and quality was observed for the regularized spectral inverse approach with pre-echo removal. The overall quality of the processed signals was highly correlated with the attribute reverberant or/and distorted. To generalize the present outcomes, further studies are needed to account for the influence of the estimation errors