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Plank T.,University of Regensburg | Rosengarth K.,University of Regensburg | Song W.,Bruel and Kjaer Vibro | Ellermeier W.,TU Darmstadt | Greenlee M.W.,University of Regensburg
Human Brain Mapping

Multisensory integration assists us to identify objects by providing multiple cues with respect to object category and spatial location. We used a semantic audiovisual object matching task to determine the effect of spatial congruency on response behavior and fMRI brain activation. Fifteen subjects responded in a four-alternative response paradigm, which visual quadrant contained the object best matched to the sound presented. Realistic sounds based on head-related transfer functions were presented binaurally with the simulated sound source corresponding to one of the four quadrants. Following a random sequence, the location of the sound corresponded to the quadrant containing the semantically congruent target on half the trials, whereas on other trials the sound arose from an incongruent location. We examined the effects of spatial congruency on response latencies, hit-rates and fMRI responses. Preliminary behavioral results revealed a significant effect of spatial congruency on response latency or performance for stimuli with noise added. In the fMRI experiment, spatial congruency had a significant effect on the BOLD response. A cluster in the right middle and superior temporal gyrus was more activated when the auditory sound sources were spatially congruent with the semantically matching visual stimulus. In an exploratory post-hoc analysis, in which we correlated the BOLD signal with the subjects' ability to locate the sound sources, we found a significant cluster in the left inferior frontal cortex, where the BOLD response increased with sound-source localization performance. Thus spatial congruency appears to enhance the semantic integration of audiovisual object information in these brain regions. © 2011 Wiley Periodicals, Inc. Source

Manvell D.,Bruel and Kjaer Vibro | Hartog Van Banda E.,Softnoise
Applied Acoustics

After over 20 years of development, noise mapping software is, today, a professional tool that is widely used by many people with different backgrounds and experience in the applications, the data and the software used. The user has the possibility to influence the quality of the result of the noise mapping process. The major factors affecting good practice include: • the user's knowledge of the standard, • the user's knowledge of the software, • documentation of software functions and its implementation of the standard, • quality assurance of software implementation, • documentation of software settings in calculation results, • the user's analysis of the quality and impact of the input data. Several methods are available to ensure good practice and improve the quality of output through such methods as standardization and documentation, training and user certification. For example, in 2006, the European Commission Working Group Assessment of Exposure to Noise produced the "Good Practice Guide for Strategic Noise Mapping and the Production of Associated Data on Noise Exposure" Version 2. This article will describe the major factors where user influences the quality of the results and the methods to ensure good practice and improving the quality of output. © 2010 Elsevier Ltd. All rights reserved. Source

Stefani A.,Technical University of Denmark | Andresen S.,Bruel and Kjaer Vibro | Yuan W.,Singapore Institute of Manufacturing Technology | Herholdt-Rasmussen N.,Ibsen Photonics A S | Bang O.,Technical University of Denmark
IEEE Photonics Technology Letters

We report on the fabrication and characterization of the first accelerometer based on a polymer optical fiber Bragg grating (FBG) for operation at both 850 and 1550 nm. The devices have a flat frequency response over a 1-kHz bandwidth and a resonance frequency of about 3 kHz. The response is linear up to at least 15 g and sensitivities as high as 19 pm/g (shift in resonance wavelength per unit acceleration) have been demonstrated. Given that 15 g corresponds to a strain of less than 0.02% and that polymer fibers have an elastic limit of more than 1%, the polymer FBG accelerometer can measure very strong accelerations. We compare with corresponding silica FBG accelerometers and demonstrate that using polymer FBGs improves the sensitivity by more than a factor of four and increases the figure of merit, defined as the sensitivity times the resonance frequency squared. © 2012 IEEE. Source

Hald J.,Bruel and Kjaer Vibro
Journal of the Acoustical Society of America

Statistically Optimized Near-field Acoustic Holography (SONAH) is a Patch Holography method, meaning that it can be applied in cases where the measurement area covers only part of the source surface. The method performs projections directly in the spatial domain, avoiding the use of spatial discrete Fourier transforms and the associated errors. First, an inverse problem is solved using regularization. For each calculation point a multiplication must then be performed with two transfer vectors - one to get the sound pressure and the other to get the particle velocity. Considering SONAH based on sound pressure measurements, existing derivations consider only pressure reconstruction when setting up the inverse problem, so the evanescent wave amplification associated with the calculation of particle velocity is not taken into account in the regularized solution of the inverse problem. The present paper introduces a scaling of the applied plane wave functions that takes the amplification into account, and it is shown that the previously published virtual source-plane retraction has almost the same effect. The effectiveness of the different solutions is verified through a set of simulated measurements. © 2014 Acoustical Society of America. Source

Antoni J.,Compiegne University of Technology | Antoni J.,University Claude Bernard Lyon 1 | Chauhan S.,Bruel and Kjaer Vibro
Journal of Sound and Vibration

Second-order blind source separation (SOBSS) has gained recent interest in operational modal analysis (OMA), since it is able to separate a set of system responses into modal coordinates from which the system poles can be extracted by single-degree-of-freedom techniques. In addition, SOBSS returns a mixing matrix whose columns are the estimates of the system mode shapes. The objective of this paper is threefold. First, a theoretical analysis of current SOBSS methods is conducted within the OMA framework and its precise conditions of applicability are established. Second, a new separation method is proposed that fixes current limitations of SOBSS: It returns estimate of complex mode shapes, it can deal with more active modes than the number of available sensors, and it shows superior performance in the case of heavily damped and/or strongly coupled modes. Third, a theoretical connection is drawn between SOBSS and stochastic subspace identification (SSI), which stands as one of the points of reference in OMA. All approaches are finally compared by means of numerical simulations. © 2012 Elsevier Ltd. All rights reserved. Source

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