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Frank M.,University of Music and Performing Arts, Graz
Proceedings of Forum Acusticum | Year: 2014

Ambisonics is a recording and reproduction method that is based on the representation of the sound field excitation as a decomposition into spherical or circular harmonics, respectively. This achieves physically accurate sound field reproduction restricted within a sweet spot in the center of a loudspeaker array in an anechoic room. However, experiments show that a perceptually defined sweet spot is far less restrictive, even with a small number of loudspeakers in non-anechoic listening rooms. In this case, Ambisonics is rather understood as a simple amplitude-panning method based on the psychoacoustic phenomenon of a phantom source as it is known from stereophony. Taking the current opportunity, this contribution gathers recent experimental results, brings them together with the concept of quality, and hereby discusses the effect of quality elements (e.g. reproduction room, number and equalization of loudspeakers, order weighting, and decoder design) on perceived quality features (e.g. localization, source width, and coloration). The discussion reveals that a physically accurate reproduction does not necessarily yield good perceived quality. For this reason, the contribution puts optimal quality elements of Ambisonics in perspective that ensure optimal sound.

Guldenschuh M.,University of Music and Performing Arts, Graz
2013 3rd International Conference on Systems and Control, ICSC 2013 | Year: 2013

The Filtered-x-Least-Mean-Square (FxLMS) is an efficient algorithm for active-noise-control-headphones. It relies on a correct model Ŝ of the secondary-path S which, in the case of headphones, is above all determined by the acoustic path form the loudspeaker to the error-microphone. If the headphones are abruptly lifted or put on, the phase of S changes more than 90° and the formerly correct model Ŝ will suddenly be wrong and the FxLMS might diverge. This paper presents three methods how the divergence of the FxLMS can be avoided. All three methods rely on laboratory measurements under different conditions from tight headphones to completely lifted headphones. First, it is shown how a stable secondary-path model can be derived from the phase information of the measurements. For the second and third method, two secondary-path models are implemented. One for the tight use case and one for the lifted headphones. The current state of the secondary-path is then detected either via an online noise-cancelling-analysis or via an infrasonic test-signal. Comparison with existing approaches shows the robust stability and efficiency of the proposed methods. © 2013 IEEE.

Frank M.,University of Music and Performing Arts, Graz
Archives of Acoustics | Year: 2013

Phantom sources are known to be perceived similar to real sound sources but with some differences. One of the differences is an increase of the perceived source width. This article discusses the perception, measurement, and modeling of source width for frontal phantom sources with different symmetrical arrangements of up to three active loudspeakers. The perceived source width is evaluated on the basis of a listening test. The test results are compared to technical measures that are applied in room acoustics: the inter-aural cross correlation coefficient (IACC) and the lateral energy fraction (LF). Adaptation of the latter measure makes it possible to predict the results by considering simultaneous sound incidence. Finally, a simple model is presented for the prediction of the perceived source width that does not require acoustic measurements as it is solely based on the loudspeaker directions and gains. Copyright © 2013 by PAN - IPPT.

Goudarzi V.,University of Music and Performing Arts, Graz
IEEE Multimedia | Year: 2015

This article presents a user-centered design approach for creating an audio interface in the context of climate science. The author's team used contextual inquiry to gather information about scientists' workflows and focus groups to assess data about the scientists' specific use of language. The goal was to realize a domain-specific sonification platform and to identify climate metaphors to build a metaphoric sound identity for the sonification. In a separate set of experiments, participants were asked to pair sound stimuli with climate terms extracted from the initial interviews and to evaluate the sound samples aesthetically. They were also asked to choose sound textures (from a given set of sounds) that best express the specific climate parameter and to rate the relevance of the sound to the metaphor. The author's team assessed correlations between climate terminology and sound stimuli for the sonification tool to improve the sound design. Results show a tendency toward natural sounds by climate scientists. © 1994-2012 IEEE.

Schmitt-Kopplin P.,Helmholtz Center for Environmental Research | Gabelica Z.,Upper Alsace University | Gougeon R.D.,University of Burgundy | Fekete A.,Helmholtz Center for Environmental Research | And 5 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

Numerous descriptions of organic molecules present in the Murchison meteorite have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, all molecular analyses were so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a nontargeted ultra-high- resolution molecular analysis of the solvent-accessible organic fraction of Murchison extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. This molecular complexity, which provides hints on heteroatoms chronological assembly, suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biologicaland biogeochemical-driven chemical space.

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