An Instrument for Measuring the Perception of Room Acoustics from the Perspective of Musicians: The Stage Acoustic Quality Inventory (STAQI)

DFG, 244251882, Raumakustik und musikalische Interpretatio

Free Space Optical Polarization De-multiplexing and Multiplexing by means of Conical Refraction

Polarization de-multiplexing and multiplexing by means of conical refraction is proposed to increase the channel capacity for free space optical communication applications. The proposed technique is based on the forward-backward optical transform occurring when a light beam propagates consecutively along the optic axes of two identical biaxial crystals with opposite orientations of their conical refraction characteristic vectors. We present experimental proof of usefulness of the conical refraction de-multiplexing and multiplexing technique by increasing in one order of magnitude the channel capacity at optical frequencies in a propagation distance of 4m

Wave-vector and polarization dependence of conical refraction

We experimentally address the wave-vector and polarization dependence of the internal conical refraction phenomenon by demonstrating that an input light beam of elliptical transverse profile refracts into two beams after passing along one of the optic axes of a biaxial crystal, i.e. it exhibits double refraction instead of refracting conically. Such double refraction is investigated by the independent rotation of a linear polarizer and a cylindrical lens. Expressions to describe the position and the intensity pattern of the refracted beams are presented and applied to predict the intensity pattern for an axicon beam propagating along the optic axis of a biaxial crystal

Polarization tailored novel vector beams based on conical refraction

Coherent vector beams with involved states of polarization (SOP) are widespread in the literature, having applications in laser processing, super-resolution imaging and particle trapping. We report novel vector beams obtained by transforming a Gaussian beam passing through a biaxial crystal, by means of the conical refraction phenomenon. We analyze both experimentally and theoretically the SOP of the different vector beams generated and demonstrate that the SOP of the input beam can be used to control both the shape and the SOP of the transformed beam. We also identify polarization singularities of such beams for the first time and demonstrate their control by the SOP of an input beam

Conical refraction healing after partially blocking the input beam

In conical refraction, when a focused Gaussian beam passes along one of the optic axes of a biaxial crystal it is transformed into a pair of concentric bright rings at the focal plane. We demonstrate both theoretically and experimentally that this transformation is hardly affected by partially blocking the Gaussian input beam with an obstacle. We analyze the influence of the size of the obstruction both on the transverse intensity pattern of the beam and on its state of polarization, which is shown to be very robust

The Influence of Room Acoustics on Solo Music Performance: An Empirical Case Study

Since the room acoustical environment has a great influence on the auditory impression of music for both audience and performers, it can be expected that musicians adjust their way of playing to the concert hall acoustics. This interdependence, frequently described by music scholars and performers, was empirically investigated for the first time under professional concert conditions. The renowned cellist Jean-Guihen Queyras was recorded during his performances of the six Suites for Violoncello Solo by Johann Sebastian Bach in seven acoustically different concert halls. Using a software-based analysis, seven performance attributes were extracted from the recordings. To determine the acoustical properties of the concert halls, measurements according to ISO 3382-1 were conducted on the stages and in the auditoria and typical acoustical parameters were calculated. Computer models of the seven halls allowed for a reconstruction of the acoustical conditions during the concerts by simulating a sound source with the directivity of a cello as well as the occupied state of the auditoria. By means of a hierarchical linear model, the influence of room acoustics on music performance was investigated in detail. Despite the numerous other external factors present in the real-world concert situations, more than half of the variance of the performance features could be explained by room acoustical parameters, providing evidence of their significant impact on the performance of music

On the dual-cone nature of the conical refraction phenomenon

In conical refraction (CR), a focused Gaussian input beam passing through a biaxial crystal and parallel to one of the optic axes is transformed into a pair of concentric bright rings split by a dark (Poggendorff) ring at the focal plane. Here, we show the generation of a CR transverse pattern that does not present the Poggendorff fine splitting at the focal plane, i.e., it forms a single light ring. This light ring is generated from a nonhomogeneously polarized input light beam obtained by using a spatially inhomogeneous polarizer that mimics the characteristic CR polarization distribution. This polarizer allows modulating the relative intensity between the two CR light cones in accordance with the recently proposed dual-cone model of the CR phenomenon. We show that the absence of interfering rings at the focal plane is caused by the selection of one of the two CR cones. (C) 2015 Optical Society of Americ

The Influence of Room Acoustics on Solo Music Performance: An Experimental Study

For the performance of music, the room surrounding the musician and his or her audience plays an important role: it acts as an acoustical transformer, modifying the sound and thus influencing the perception of player and listeners. For the active performer, this entails a complex interaction between the production and perception of sound. The aim of this experimental study was to investigate the effect of specific room acoustical conditions on aspects of music performance such as “tempo,” “loudness,” “dynamic bandwidth,” or “timbre.” Computer models of 14 rooms were generated, corresponding to real halls and representing typical concert venues. Simulated measurements were carried out to determine room acoustical parameters according to ISO 3382–1 as well as new parameters for stage acoustics. Solo performers were recorded while playing in corresponding virtual acoustic environments generated by dynamic binaural synthesis. From these recordings, audio features were extracted to calculate descriptors for different attributes of the musical performance. The influence of room acoustical parameters on performance properties as well as the effect of the musical content and the played instrument was then analyzed based on hierarchical linear models. The analysis revealed distinct concepts of adjustment to room acoustical conditions as well as great individuality with respect to the interaction of musicians with their room acoustical environment.DFG, 244251882, Raumakustik und musikalische Interpretation: Neue Parameter für die akustischen Verhältnisse auf Bühne

Interferometric characterization of the structured polarized light beam produced by the conical refraction phenomenon

The interest on the conical refraction (CR) phenomenon in biaxial crystals has revived in the last years due to its prospective for generating structured polarized light beams, i.e. vector beams. While the intensity and the polarization structure of the CR beams are well known, an accurate experimental study of their phase structure has not been yet carried out. We investigate the phase structure of the CR rings by means of a Mach-Zehnder interferometer while applying the phase-shifting interferometric technique to measure the phase at the focal plane. In general the two beams interfering correspond to different states of polarization (SOP) which locally vary. To distinguish if there is an additional phase added to the geometrical one we have derived the appropriate theoretical expressions using the Jones matrix formalism. We demonstrate that the phase of the CR rings is equivalent to that one introduced by an azimuthally segmented polarizer with CR-like polarization distribution. Additionally, we obtain direct evidence that the Poggendorff dark ring is an annular singularity, with a π phase change between the inner and outer bright rings.We acknowledge financial support from the Spanish MINECO and Fondos FEDER (FIS2012-39158-C02-01, FIS2011-23719, BES-2010-031696, and AP2010-2310), and the Catalan Government (2014 SGR 1639). C. Iemmi appreciates the support from UBACyT 20020100100689, CONICET PIP 112-200801-03047, and ANPCYT PICT 2010-02179 (Argentina)