This paper builds on the idea of frequency bin-wise separation of mixed speech signals by Gaussian Mixture Model fitting using the Expectation-Maximization algorithm on Phase-Difference-of-Arrival values between two microphones. We find that using a combination of pre-processing steps and error finding post processing, separation performance exceeding the state of the art is achieved on publicly available live recording data.

LEVI, A., H. BELOEV and N. KOLEV, 2013. On the biaxial distribution of anisotropic elastic modulus of thin-plate polycrystalline elements and his identification in agricultural machinery with ultrasonic methods. Bulg. J. Agric. Sci., 19: 383-386 A new method for identification of texture in agricultural machinery with interpolation of biaxial anisotropy of elastic modulus of thin-plate polycrystalline elements has been developed. The dependence of shear modulus and modulus of longitudinal elasticity as a function of an angular distribution of Poisson’s ratio, achieved by the method of ulrasonic critical-angle refractometry (UCR), has been derived.

The paper includes results of joint aeroplane remote sensing and synchronous ground-based studies for estimation of the state of the system "soil-plant-surface air layer" on the agricultural areas for management of agricultural activities on the field. The methods of study include expedition trace flights of an aeroplane-laboratory along several routes over the Bassarbovo agricultural test region near Russe, Bulgaria, measurements of the radiobrightness temperature with a radiometric system and temperature in the infrared range of soil and vegetation cover in dry and wet days during the active agricultural season. The obtained soil arid crop water content and temperature maps of the agricultural areas reveal a qualitative difference between dry and wet conditions of soil surface and crop canopy. Having the data and information collected by observations and measurements, agronomists can monitor the dynamics of the processes in the field and their influence on crop growth, plant diseases, insect activity, crop water stress, etc.

According to a new theory poycrystal elements are a comlex self-organized system which gives the possibility to modulate the processes of strengthening by changing temperature within a wide range. An unconventional method for non-destructive determination of the minimal operating temperature (ductile to brittle transition temperature of structural steel T-DBTT), based on the results of measuring the speeds of longitudinal and transversal ultrasonic waves and the achieved values of Poisson's ratio, has been developed.

The paper considers one of the few studies on polycrystal continuum as a dissipation system. The analysis of polycrystal continuum as a complex self-organized dissipation system leads to a nonlinear differential equation of second kind which depends on three rheological constants. By lowering the kind we receive a mathematical module describing the processes of strengthening and of the evaluation ultimate stress ratio (relation of ultimate stress in tension and compression).

Beamforming techniques are applied to microphone arrays with the aim of separating sources and improving intelligibility, by means of spatial filtering. The non-stationary nature of speech implies the use of adaptive beamformers and several solutions have been implemented. Furthermore, interfering signals coming from the same direction as the target signal, cannot be filtered by the beamformer. The method presented in this paper is an alternative to adaptive beamforming, combining a simple delay-and-sum beamformer with a time-frequency masking method based on phase information. The beamformer is steered to the desired source and a function related to the phase differences between the steered signals at the microphones is evaluated to reject any interference that passed through the beamformer. Thus, the algorithm does not need to constantly adapt the filter coefficients and takes advantage of both beamforming properties and time-frequency separation techniques. The separation performance of the method has been evaluated in a noisy and reverberant environment using different arrays, talkers and scenarios. Real data are used to show the performance of the real-time algorithm when isolating one of the sources in the mixture.

An important application for microphone arrays is to extract high-quality output from a single wideband source in multi-source and adverse environments. Methods based on blind-source separation and beamforming have been proposed in the literature. In this paper, we propose a new algorithm for isolating sources which may be considered an alternate approach to adaptive beamforming. The proposed method assigns every time-frequency point to one of the sources in the environment or as background noise using an SRP-PHAT-based discriminator. It then creates the desired source's output by spectrally subtracting the inappropriate time-frequency points. After giving the details of the procedure, we show results from real data from our large-aperture microphone array. Though, clearly a relatively small subset, listening results to date for two or three talkers have yielded high-quality isolations. For two talkers, in particular, results are presented which indicate that the method correctly identifies and removes about 90% of those time-frequency points where the interfering signal is dominant, without affecting the desired signal significantly.

Knowing the orientation of a talker in the focal area of a large-aperture microphone array enables the development of better beamforming algorithms (to obtain higher-quality speech output), improves source-location/tracking algorithms, and allows better selection and control of cameras in a video conference situation. Measurements in an anechoic room (e.g., Chu and Warnock, 2002) have quantified the average frequency-dependent magnitude (source radiation pattern) of the human speech source showing a front-to-back difference in magnitude that increases with frequency by about 8 dB/decade reaching about 18 dB at 8000 Hz. These amplitude differences, while severely masked by both coherent and noncoherent noise in a real environment, are the most extractable phenomena from a talker's orientation when compared to other phenomena such as phase differences due to the source or effects due to diffraction at the mouth. In this paper, we propose a robust, source-radiation-pattern-based method for extraction of the azimuth angle of a single talker for whom an accurate point-source location estimate is known. The method requires no a priori training and has been tested in more than 100 situations with real human talkers having various locations and orientations in a room equipped with a large aperture microphone array. We compare these results against earlier published algorithms and find that the method proposed herein is the most robust and is sufficient to be considered for a real time system.

An adaptive learning technology embedded in e-learning environments ensures choice of the structure, content, and activities for each individual learner according to the teaching team’s domain and didactic knowledge and skills. In this paper a computer-based scenario for application of an adaptive navigation technology is proposed and demonstrated on an example course topic.

Knowing the orientation of a talker allows a a large-aperture microphone array to select and control cameras better in a teleconferencing situation, improve source-location estimation, and, often, improve beamforming. In 2004, we introduced a baseline algorithm for determining orientation azimuth. Recent testing showed the baseline algorithm behaved poorly when the source was not in the center of the focal area for the array. Here, we describe a second-generation algorithm, A2, that has overcome many of the baselinepsilas short-falls. It still extracts the estimate from microphone energies, but is improved by 1) using a narrow-band, high-frequency analysis, rather than the broad band of the baseline algorithm, 2) using spectral subtraction for uncorrelated noise removal and 3) fitting the processed microphone energies to an ideal model for the direct-wave energy. Most important is that 3) incorporates inverse-square-law effects properly on the direct wave only, which was not the case in the baseline. Results from an advanced simulator are presented to illustrate the issues. Then, A2 and baseline algorithm results are compared using about 60 direct recordings from a human talker in a typical and noisy environment using our 448-microphone array. These show that A2 is a significant improvement.