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Spectral Domain Speech Enhancement Using HMM State-Dependent Super-Gaussian Priors
KTH, School of Electrical Engineering (EES), Sound and Image Processing.
Ruhr-University Bochum.
KTH, School of Electrical Engineering (EES), Sound and Image Processing.
2013 (English)In: IEEE Signal Processing Letters, ISSN 1070-9908, E-ISSN 1558-2361, Vol. 20, no 3, 253-256 p.Article in journal (Refereed) Published
Abstract [en]

The derivation of MMSE estimators for the DFT coefficients of speech signals, given an observed noisy signal and super-Gaussian prior distributions, has received a lot of interest recently. In this letter, we look at the distribution of the periodogram coefficients of different phonemes, and show that they have a gamma distribution with shape parameters less than one. This verifies that the DFT coefficients for not only the whole speech signal but also for individual phonemes have super-Gaussian distributions. We develop a spectral domain speech enhancement algorithm, and derive hidden Markov model (HMM) based MMSE estimators for speech periodogram coefficients under this gamma assumption in both a high uniform resolution and a reduced-resolution Mel domain. The simulations show that the performance is improved using a gamma distribution compared to the exponential case. Moreover, we show that, even though beneficial in some aspects, the Mel-domain processing does not lead to better results than the algorithms in the high-resolution domain.

Place, publisher, year, edition, pages
IEEE Signal Processing Society, 2013. Vol. 20, no 3, 253-256 p.
Keyword [en]
HMM, speech enhancement, super-Gaussian pdf
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
URN: urn:nbn:se:kth:diva-118490DOI: 10.1109/LSP.2013.2242467ISI: 000314828600002ScopusID: 2-s2.0-84873620144OAI: diva2:606567

QC 20130221

Available from: 2013-02-21 Created: 2013-02-19 Last updated: 2013-09-16Bibliographically approved
In thesis
1. Speech Enhancement Using Nonnegative MatrixFactorization and Hidden Markov Models
Open this publication in new window or tab >>Speech Enhancement Using Nonnegative MatrixFactorization and Hidden Markov Models
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Reducing interference noise in a noisy speech recording has been a challenging task for many years yet has a variety of applications, for example, in handsfree mobile communications, in speech recognition, and in hearing aids. Traditional single-channel noise reduction schemes, such as Wiener filtering, do not work satisfactorily in the presence of non-stationary background noise. Alternatively, supervised approaches, where the noise type is known in advance, lead to higher-quality enhanced speech signals. This dissertation proposes supervised and unsupervised single-channel noise reduction algorithms. We consider two classes of methods for this purpose: approaches based on nonnegative matrix factorization (NMF) and methods based on hidden Markov models (HMM).

 The contributions of this dissertation can be divided into three main (overlapping) parts. First, we propose NMF-based enhancement approaches that use temporal dependencies of the speech signals. In a standard NMF, the important temporal correlations between consecutive short-time frames are ignored. We propose both continuous and discrete state-space nonnegative dynamical models. These approaches are used to describe the dynamics of the NMF coefficients or activations. We derive optimal minimum mean squared error (MMSE) or linear MMSE estimates of the speech signal using the probabilistic formulations of NMF. Our experiments show that using temporal dynamics in the NMF-based denoising systems improves the performance greatly. Additionally, this dissertation proposes an approach to learn the noise basis matrix online from the noisy observations. This relaxes the assumption of an a-priori specified noise type and enables us to use the NMF-based denoising method in an unsupervised manner. Our experiments show that the proposed approach with online noise basis learning considerably outperforms state-of-the-art methods in different noise conditions.

 Second, this thesis proposes two methods for NMF-based separation of sources with similar dictionaries. We suggest a nonnegative HMM (NHMM) for babble noise that is derived from a speech HMM. In this approach, speech and babble signals share the same basis vectors, whereas the activation of the basis vectors are different for the two signals over time. We derive an MMSE estimator for the clean speech signal using the proposed NHMM. The objective evaluations and performed subjective listening test show that the proposed babble model and the final noise reduction algorithm outperform the conventional methods noticeably. Moreover, the dissertation proposes another solution to separate a desired source from a mixture with arbitrarily low artifacts.

 Third, an HMM-based algorithm to enhance the speech spectra using super-Gaussian priors is proposed. Our experiments show that speech discrete Fourier transform (DFT) coefficients have super-Gaussian rather than Gaussian distributions even if we limit the speech data to come from a specific phoneme. We derive a new MMSE estimator for the speech spectra that uses super-Gaussian priors. The results of our evaluations using the developed noise reduction algorithm support the super-Gaussianity hypothesis.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xiv, 52 p.
Trita-EE, ISSN 1653-5146 ; 2013:030
Speech enhancement, noise reduction, nonnegative matrix factorization, hidden Markov model, probabilistic latent component analysis, online dictionary learning, super-Gaussian distribution, MMSE estimator, temporal dependencies, dynamic NMF
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-124642 (URN)978-91-7501-833-1 (ISBN)
Public defence
2013-10-18, Lecture Room F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)

QC 20130916

Available from: 2013-09-16 Created: 2013-07-24 Last updated: 2013-10-09Bibliographically approved

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