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Journal Article•

Mathematical Analysis of Random Noise-Conclusion

01 Jan 1945-Bell System Technical Journal-Vol. 24, pp 46-156
About: This article is published in Bell System Technical Journal.The article was published on 1945-01-01 and is currently open access. It has received 807 citations till now.
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TL;DR: In this article, a simple three-parameter distribution family is suggested such that it possesses the exact mean for smooth wide band processes with simple auto-dependence properties of Markov type.

22 citations

DOI•
01 Jan 2006
TL;DR: In this paper, the authors propose to discretize the physical space into a few sectors, and for each time frame, to determine which sectors contain active acoustic sources (Where? When?) and to locate precisely a speaker within an active sector.
Abstract: Accurate detection, localization and tracking of multiple moving speakers permits a wide spectrum of applications Techniques are required that are versatile, robust to environmental variations, and not constraining for non-technical end-users Based on distant recording of spontaneous multiparty conversations, this thesis focuses on the use of microphone arrays to address the question Who spoke where and when? The speed, the versatility and the robustness of the proposed techniques are tested on a variety of real indoor recordings, including multiple moving speakers as well as seated speakers in meetings Optimized implementations are provided in most cases We propose to discretize the physical space into a few sectors, and for each time frame, to determine which sectors contain active acoustic sources (Where? When?) A topological interpretation of beamforming is proposed, which permits both to evaluate the average acoustic energy in a sector for a negligible cost, and to locate precisely a speaker within an active sector One additional contribution that goes beyond the eld of microphone arrays is a generic, automatic threshold selection method, which does not require any training data On the speaker detection task, the new approach is dramatically superior to the more classical approach where a threshold is set on training data We use the new approach into an integrated system for multispeaker detection-localization Another generic contribution is a principled, threshold-free, framework for short-term clustering of multispeaker location estimates, which also permits to detect where and when multiple trajectories intersect On multi-party meeting recordings, using distant microphones only, short-term clustering yields a speaker segmentation performance similar to that of close-talking microphones The resulting short speech segments are then grouped into speaker clusters (Who?), through an extension of the Bayesian Information Criterion to merge multiple modalities On meeting recordings, the speaker clustering performance is signicantly improved by merging the classical mel-cepstrum information with the short-term speaker location information Finally, a close analysis of the speaker clustering results suggests that future research should investigate the effect of human acoustic radiation characteristics on the overall transmission channel, when a speaker is a few meters away from a microphone

22 citations

Journal Article•DOI•
TL;DR: In this paper, the photoelectron counting distribution for a two-photon detector is derived quantum mechanically assuming that the ionising transitions in the atoms of the detector take place through the simultaneous absorption of two photons.
Abstract: A formula for the photoelectron-counting distribution for a two-photon detector is derived quantum mechanically assuming that the ionising transitions in the atoms of the detector take place through the simultaneous absorption of two photons. It is assumed that the incident light is quasimonochromatic. It is shown that the distribution of the photoelectrons is given by the average of a Poisson distribution, the parameter of the distribution being proportional to the time integral of the square of the instantaneous light intensity. Counting distributions for the thermal (gaussian) light and for some models of laser light are obtained for the limiting case when the counting-time interval T is short compared to the coherence time Tc of the light. An approximate formula for arbitrary time intervals for the counting distribution of thermal light is also proposed.

22 citations

Journal Article•DOI•
TL;DR: In this article, the authors studied the number of points where the gradient of a stationary Gaussian random field restricted to a compact set in R d takes a fixed value, and they extended to higher dimensions the Geman condition, a sufficient condition on covariance function under which the variance of this random variable is finite.

22 citations

Journal Article•DOI•
TL;DR: A three-dimensional, space-frequency theory is developed for the analysis and simulation of radiation excitation and propagation in electron devices and free-electron lasers operating in an ultrawide range of frequencies.
Abstract: The principle of operation of intense radiation devices such as microwave tubes, free-electron lasers, and masers, is based on a distributed interaction between an electron beam and electromagnetic radiation. Some of the effects emerging during the interaction involve a continuum of frequencies in their broadband spectrum. We developed a three-dimensional, space-frequency theory for the analysis and simulation of radiation excitation and propagation in electron devices and free-electron lasers operating in an ultrawide range of frequencies. The total electromagnetic field (radiation and space-charge waves) is presented in the frequency domain as an expansion in terms of transverse eigenmodes of the (cold) cavity, in which the field is excited and propagates. The mutual interaction between the electron beam and the electromagnetic field is fully described by coupled equations, expressing the evolution of mode amplitudes and electron beam dynamics. The approach is applied in a numerical particle code WB3D, simulating wideband interactions in free-electron lasers operating in the linear and nonlinear regimes.

22 citations