A recursive expectation-maximization algorithm for speaker tracking and separation

The problem of blind and online speaker localization and separation using multiple microphones is addressed based on the recursive expectation-maximization (REM) procedure. A two-stage REM-based algorithm is proposed: (1) multi-speaker direction of arrival (DOA) estimation and (2) multi-speaker relative transfer function (RTF) estimation. The DOA estimation task uses only the time frequency (TF) bins dominated by a single speaker while the entire frequency range is not required to accomplish this task. In contrast, the RTF estimation task requires the entire frequency range in order to estimate the RTF for each frequency bin. Accordingly, a different statistical model is used for the two tasks. The first REM model is applied under the assumption that the speech signal is sparse in the TF domain, and utilizes a mixture of Gaussians (MoG) model to identify the TF bins associated with a single dominant speaker. The corresponding DOAs are estimated using these bins. The second REM model is applied under the assumption that the speakers are concurrently active in all TF bins and consequently applies a multichannel Wiener filter (MCWF) to separate the speakers. As a result of the assumption of the concurrent speakers, a more precise TF map of the speakers’ activity is obtained. The RTFs are estimated using the outputs of the MCWF-beamformer (BF), which are constructed using the DOAs obtained in the previous stage. Next, using the linearly constrained minimum variance (LCMV)-BF that utilizes the estimated RTFs, the speech signals are separated. The algorithm is evaluated using real-life scenarios of two speakers. Evaluation of the mean absolute error (MAE) of the estimated DOAs and the separation capabilities, demonstrates significant improvement w.r.t. a baseline DOA estimation and speaker separation algorithm.

Validity of a theoretical model to examine blood oxygenation dependent optoacoustics

A theoretical model investigating the dependence of optoacoustic (OA) signal on blood oxygen saturation (SO2) is discussed. The derivations for the nonbandlimited and bandlimited OA signals from many red blood cells (RBCs) are presented. The OA field generated by many RBCs was obtained by summing the OA field emitted by each RBC approximated as a fluid sphere. A Monte Carlo technique was employed generating the spatial organizations of RBCs in two-dimensional. The RBCs were assumed to have the same SO2 level in a simulated configuration. The fractional number of oxyhemoglobin molecules, confined in a cell, determined the cellular SO2 and also defined the blood SO2. For the nonbandlimited case, the OA signal amplitude decreased and increased linearly with blood SO2 when illuminated by 700 and 1000 nm radiations, respectively. The power spectra exhibited similar trends over the entire frequency range (MHz to GHz). For the bandlimited case, three acoustic receivers with 2, 10, and 50 MHz as the center frequencies were considered. The linear variations of the OA amplitude with blood SO2 were also observed for each receiver at those laser sources. The good agreement between simulated and published experimental results validates the model qualitatively.

A Compact Low-Profile High Isolation MIMO Antenna For X-Band Applications

A novel compact low profile MIMO antenna is designed and implemented with high isolation for the X band applications. Proposed MIMO geometry is incorporated with two monopoles which are excited by 50 Ω feed line. To enhance the isolation between inter-elements meander line structures are is identically placed. These meander line structures are reducing the mutual coupling up to 26 dB. In the proposed MIMO antenna two elements cover the entire frequency range between 7.4-11.8 GHz for the X band applications. Meander line structure is working as a decoupling network which improves the isolation considerably. The overall size of the MIMO antenna is 25 × 30 × 1 mm3, and it offers inter-element isolation of >26 dB, envelope correlation coefficient is less than 0.2, and directivity gain >9.99 over the resonating frequency range. The proposed MIMO antenna model is fabricated, and measurement results are verified with simulated results. The antenna shows the satisfactory gain of around 4.8 dB in entire frequency range. The antenna shows the satisfactory gain of around 4.5 dB in entire frequency range.

Validity of a theoretical model to examine blood oxygenation dependent optoacoustics

A theoretical model investigating the dependence of optoacoustic (OA) signal on blood oxygen saturation (SO2) is discussed. The derivations for the nonbandlimited and bandlimited OA signals from many red blood cells (RBCs) are presented. The OA field generated by many RBCs was obtained by summing the OA field emitted by each RBC approximated as a fluid sphere. A Monte Carlo technique was employed generating the spatial organizations of RBCs in two-dimensional. The RBCs were assumed to have the same SO2 level in a simulated configuration. The fractional number of oxyhemoglobin molecules, confined in a cell, determined the cellular SO2 and also defined the blood SO2. For the nonbandlimited case, the OA signal amplitude decreased and increased linearly with blood SO2 when illuminated by 700 and 1000 nm radiations, respectively. The power spectra exhibited similar trends over the entire frequency range (MHz to GHz). For the bandlimited case, three acoustic receivers with 2, 10, and 50 MHz as the center frequencies were considered. The linear variations of the OA amplitude with blood SO2 were also observed for each receiver at those laser sources. The good agreement between simulated and published experimental results validates the model qualitatively.

Validity of a theoretical model to examine blood oxygenation dependent optoacoustics

A theoretical model investigating the dependence of optoacoustic (OA) signal on blood oxygen saturation (SO2) is discussed. The derivations for the nonbandlimited and bandlimited OA signals from many red blood cells (RBCs) are presented. The OA field generated by many RBCs was obtained by summing the OA field emitted by each RBC approximated as a fluid sphere. A Monte Carlo technique was employed generating the spatial organizations of RBCs in two-dimensional. The RBCs were assumed to have the same SO2 level in a simulated configuration. The fractional number of oxyhemoglobin molecules, confined in a cell, determined the cellular SO2 and also defined the blood SO2. For the nonbandlimited case, the OA signal amplitude decreased and increased linearly with blood SO2 when illuminated by 700 and 1000 nm radiations, respectively. The power spectra exhibited similar trends over the entire frequency range (MHz to GHz). For the bandlimited case, three acoustic receivers with 2, 10, and 50 MHz as the center frequencies were considered. The linear variations of the OA amplitude with blood SO2 were also observed for each receiver at those laser sources. The good agreement between simulated and published experimental results validates the model qualitatively.

Evidence that the Dorsal Velvet of Barn Owl Wing Feathers Decreases Rubbing Sounds during Flapping Flight

Synopsis Owls have specialized feather features hypothesized to reduce sound produced during flight. One of these features is the velvet, a structure composed of elongated filaments termed pennulae that project dorsally from the upper surface of wing and tail feathers. There are two hypotheses of how the velvet functions to reduce sound. According to the aerodynamic noise hypothesis, the velvet reduces sound produced by aerodynamic processes, such as turbulence development on the surface of the wing. Alternatively, under the structural noise hypothesis, the velvet reduces frictional noise produced when two feathers rub together. The aerodynamic noise hypothesis predicts impairing the velvet will increase aerodynamic flight sounds predominantly at low frequency, since turbulence formation predominantly generates low frequency sound; and that changes in sound levels will occur predominantly during the downstroke, when aerodynamic forces are greatest. Conversely, the frictional noise hypothesis predicts impairing the velvet will cause a broadband (i.e., across all frequencies) increase in flight sounds, since frictional sounds are broadband; and that changes in sound levels will occur during the upstroke, when the wing feathers rub against each other the most. Here, we tested these hypotheses by impairing with hairspray the velvet on inner wing feathers (P1-S4) of 13 live barn owls (Tyto alba) and measuring the sound produced between 0.1 and 16 kHz during flapping flight. Relative to control flights, impairing the velvet increased sound produced across the entire frequency range (i.e., the effect was broadband) and the upstroke increased more than the downstroke, such that the upstroke of manipulated birds was louder than the downstroke, supporting the frictional noise hypothesis. Our results suggest that a substantial amount of bird flight sound is produced by feathers rubbing against feathers during flapping flight.

Long Range Backhaul Microwave Connectivity in Wireless Sensor Networks via a New Antenna Designed for ISM 2.4 GHz Band

This study aimed to explore a metallic striped grid array planar antenna, analyze it numerically in terms of its parameters, and optimize it for best performance. It may be an appropriate candidate for long-range point-to-point connectivity in wireless sensor networks. Antenna gain and frequency impedance bandwidth are two important performance parameters. For an efficient antenna, its gain should be high while maintaining operating bandwidth wide enough to accommodate the entire frequency range for which it has been designed. Concurrently, antenna size should also be small. In this study, antenna dimensions were kept as small as possible without compromising its performance. Its dimensions were 300 mm × 210 mm × 9.9 mm, which made it compact and miniature. It had a maximum gain of 16.72 dB at 2.45 GHz and maximum frequency impedance bandwidth of 7.68% relative to 50 Ω. It operated across a frequency band ranging from 2.38 GHz to 2.57 GHz, encapsulating the entire ISM 2.4 GHz band. Its radiation efficiency remained above 93% in this band with a maximum of 98.5% at 2.45 GHz. Moreover, it also had narrow HPBWs in horizontal and vertical planes having values of 18.52° and 31.25°, respectively.

Dual-Band Circularly Polarized Dielectric Resonator Antenna for WLAN and WiMAX Applications

In this paper, a new dual-band circularly polarized (CP) dielectric resonator antenna for WLAN and WiMAX applications is proposed. The dielectric resonator has an asymmetric Y-shaped geometry. By properly selecting the length of the arms, the pairs of fundamental (TE 111 ) and second-order (TE 211 ) are excited separately at the design frequencies to radiate the CP wave. The measurement shows that the fabricated antenna exhibits a wide impedance bandwidth for |S 11 | < −10 dB of 62.07% (2.2–4.18 GHz). The far-field measurements in the broadside direction demonstrated a dual-band CP response with 3 dB ARBWs of 4.92%(2.38–2.5 GHz) at the lower and 12.64% (3.26–3.70 GHz) at the upper band. The measured CP bands cover the entire frequency range of WLAN (2.401–2.495 GHz) and WiMAX (3.4–3.69 GHz) at the lower and upper bands, respectively.

A Multiband Arrow Shaped Patch Antenna Based on Apollonian Gasket and Soddy’s circle for Application in LTE and UWB range

A novel arrow shaped planar multiband antenna based on apollonian gasket and Soddy’s circle with Defective Ground Structure (DGS) is described in this paper. The structure is designed on an FR4_epoxy substrate (εr=4.4).The performance is evaluated using HFSS software. The antenna displays multiband behaviour in the frequency range from 3 to 10 GHz which is suitable for wireless communications applications.The antenna gives tri-frequency response in LTE range(600 MHz6GHz):1.17 GHz, 3.44 GHz and 6 GHz;and tetra frequency response in the UWB frequency range(3 GHz to 10 GHz): 8.1 GHz, 9.5 GHz, 11.8 GHz & 13.5 GHz which could be used in wireless and radar communications.The overall performance of the antenna demonstrates an average impedance bandwidth(IBW) of 300 MHz with a good impedance matching (S11< -10 dB).The proposed antenna has the satisfactory radiation characteristics throughout its operating band. The measured highest gain differs from 1 dBi to 1.9 dBi inthe entire frequency range.

Development of materials obtained from recycled cars and their subsequent use in noise reduction

In terms of design and material composition, cars are the large set of diverse materials and raw materials. The relative proportion of materials varies along with the development and innovation of new types of cars. The most represented material is metal. On average, outdated cars feature about 8% of plastic and approximately 4% of rubber products. The problem is the further use of these recycled materials. The research has found new areas for the use of tires, waste foam and interior materials—noise reduction. The authors have designed and tested several variations of acoustic absorption materials. Of the tested materials, the best parameters were shown by “ecofoam”—almost across the entire frequency range (100–5000 Hz).