Structured Sparsity Models for Multiparty Speech Recovery from Reverberant Recordings

We tackle the multi-party speech recovery problem through modeling the acoustic of the reverberant chambers. Our approach exploits structured sparsity models to perform room modeling and speech recovery. We propose a scheme for characterizing the room acoustic from the unknown competing speech sources relying on localization of the early images of the speakers by sparse approximation of the spatial spectra of the virtual sources in a free-space model. The images are then clustered exploiting the low-rank structure of the spectro-temporal components belonging to each source. This enables us to identify the early support of the room impulse response function and its unique map to the room geometry. To further tackle the ambiguity of the reflection ratios, we propose a novel formulation of the reverberation model and estimate the absorption coefficients through a convex optimization exploiting joint sparsity model formulated upon spatio-spectral sparsity of concurrent speech representation. The acoustic parameters are then incorporated for separating individual speech signals through either structured sparse recovery or inverse filtering the acoustic channels. The experiments conducted on real data recordings demonstrate the effectiveness of the proposed approach for multi-party speech recovery and recognition.Comment: 31 page

Attosecond Streaking in the Water Window: A New Regime of Attosecond Pulse Characterization

We report on the first streaking measurement of water-window attosecond pulses generated via high harmonic generation, driven by sub-2-cycle, CEP-stable, 1850 nm laser pulses. Both the central photon energy and the energy bandwidth far exceed what has been demonstrated thus far, warranting the investigation of the attosecond streaking technique for the soft X-ray regime and the limits of the FROGCRAB retrieval algorithm under such conditions. We also discuss the problem of attochirp compensation and issues regarding much lower photo-ionization cross sections compared with the XUV in addition to the fact that several shells of target gases are accessed simultaneously. Based on our investigation, we caution that the vastly different conditions in the soft X-ray regime warrant a diligent examination of the fidelity of the measurement and the retrieval procedure.Comment: 14 Pages, 12 figure

Localization of Sound Sources in a Room with One Microphone

Estimation of the location of sound sources is usually done using microphone arrays. Such settings provide an environment where we know the difference between the received signals among different microphones in the terms of phase or attenuation, which enables localization of the sound sources. In our solution we exploit the properties of the room transfer function in order to localize a sound source inside a room with only one microphone. The shape of the room and the position of the microphone are assumed to be known. The design guidelines and limitations of the sensing matrix are given. Implementation is based on the sparsity in the terms of voxels in a room that are occupied by a source. What is especially interesting about our solution is that we provide localization of the sound sources not only in the horizontal plane, but in the terms of the 3D coordinates inside the room

On-chip spectropolarimetry by fingerprinting with random surface arrays of nanoparticles

Optical metasurfaces revolutionized the approach to moulding the propagation of light by enabling simultaneous control of the light phase, momentum, amplitude and polarization. Thus, instantaneous spectropolarimetry became possible by conducting parallel intensity measurements of differently diffracted optical beams. Various implementations of this very important functionality have one feature in common - the determination of wavelength utilizes dispersion of the diffraction angle, requiring tracking the diffracted beams in space. Realization of on-chip spectropolarimetry calls thereby for conceptually different approaches. In this work, we demonstrate that random nanoparticle arrays on metal surfaces, enabling strong multiple scattering of surface plasmon polaritons (SPPs), produce upon illumination complicated SPP scattered patterns, whose angular spectra are uniquely determined by the polarization and wavelength of light, representing thereby spectropolarimetric fingerprints. Using um-sized circular arrays of randomly distributed {\mu}m-sized gold nanoparticles (density ~ 75 {\mu}m$^-$$^2$}) fabricated on gold films, we measure angular distributions of scattered SPP waves using the leakage radiation microscopy and find that the angular SPP spectra obtained for normally incident light beams different in wavelength and/or polarization are distinctly different. Our approach allows one to realize on-chip spectropolarimetry by fingerprinting using surface nanostructures fabricated with simple one-step electron-beam lithography.Comment: 22 pages, 5 figure

Investigations on electromagnetic noises and interactions in electronic architectures : a tutorial case on a mobile system

Electromagnetic interactions become critic in embedded and smart electronic structures. The increase of electronic performances confined in a finite volume or support for mobile applications defines new electromagnetic environment and compatibility configurations (EMC). With canonical demonstrators developed for tutorials and EMC experiences, this paper present basic principles and experimental techniques to investigate and control these severe interferences. Some issues are reviewed to present actual and future scientific challenges for EMC at electronic circuit level

Sampling Sparse Signals on the Sphere: Algorithms and Applications

We propose a sampling scheme that can perfectly reconstruct a collection of spikes on the sphere from samples of their lowpass-filtered observations. Central to our algorithm is a generalization of the annihilating filter method, a tool widely used in array signal processing and finite-rate-of-innovation (FRI) sampling. The proposed algorithm can reconstruct $K$ spikes from $(K+\sqrt{K})^2$ spatial samples. This sampling requirement improves over previously known FRI sampling schemes on the sphere by a factor of four for large $K$. We showcase the versatility of the proposed algorithm by applying it to three different problems: 1) sampling diffusion processes induced by localized sources on the sphere, 2) shot noise removal, and 3) sound source localization (SSL) by a spherical microphone array. In particular, we show how SSL can be reformulated as a spherical sparse sampling problem.Comment: 14 pages, 8 figures, submitted to IEEE Transactions on Signal Processin

Gain assisted harmonic generation in near-zero permittivity metamaterials made of plasmonic nanoshells

We investigate enhanced harmonic generation processes in gain-assisted, near-zero permittivity metamaterials composed of spherical plasmonic nanoshells. We report the presence of narrow-band features in transmission, reflection and absorption induced by the presence of an active material inside the core of the nanoshells. The damping-compensation mechanism used to achieve the near-zero effective permittivity condition also induces a significant increase in field localization and strength and, consequently, enhancement of linear absorption. When only metal nonlinearities are considered, second and third harmonic generation efficiencies obtained by probing the structure in the vicinity of the near-zero permittivity condition approach values as high as for irradiance value as low as . These results clearly demonstrate that a relatively straightforward path now exists to the development of exotic and extreme nonlinear optical phenomena in the KW/cm2 rang

Purely nonlinear disorder-induced localizations and their parametric amplification

We investigate spatial localization in a quadratic nonlinear medium in the presence of randomness. By means of numerical simulations and theoretical analyses we show that, in the down conversion regime, the transverse random modulation of the nonlinear susceptibility generates localizations of the fundamental wave that grow exponentially in propagation. The localization length is optically controlled by the pump intensity which determines the amplification rate. The results also apply to cubic nonlinearities.Comment: 5 pages, 5 figure