scholarly journals Design, Control, and Evaluation of Mixed-Order, Compact Spherical Loudspeaker Arrays

2020 ◽  
Vol 44 (4) ◽  
pp. 60-76
Author(s):  
Stefan Riedel ◽  
Franz Zotter
Keyword(s):  
Horizontal Plane ◽  
Electroacoustic Music ◽  
High Frequencies ◽  
Horizontal Beam ◽  
Sound Beams ◽  
Mixed Order ◽  
Auditory Object ◽  
Analytic Models ◽  
Object Trajectories ◽  
Beam Patterns

Abstract Beamforming on the icosahedral loudspeaker (IKO), a compact, spherical loudspeaker array, was recently established and investigated as an instrument to produce auditory sculptures (i.e., 3-D sonic imagery) in electroacoustic music. Sound beams in the horizontal plane most effectively and expressively produce auditory objects via lateral reflections on sufficiently close walls and baffles. Can there be 3-D-printable arrays at drastically reduced cost and transducer count, but with similarly strong directivity in the horizontal plane? To find out, we adopt mixed-order Ambisonics schemes to control fewer, and predominantly horizontal, beam patterns, and we propose the 3|9|3 array as a suitable design, with beamforming crossing over to Ambisonics panning at high frequencies. Analytic models and measurements on hardware prototypes permit a comparison between the new design and the IKO regarding beamforming capacity. Moreover, we evaluate our 15-channel 3|9|3 prototype in listening experiments to find out whether the sculptural qualities and auditory object trajectories it produces are comparable to those of the 20-channel IKO.

scholarly journals Beam Patterns of the Five-hundred-metre Aperture Spherical Telescope

2013 ◽  
Vol 30 ◽  
Author(s):  
B. Dong ◽  
J. L. Han
Keyword(s):  
Structural Parameters ◽  
Power Level ◽  
Three Dimensional ◽  
High Gain ◽  
Main Beam ◽  
Frequency Range ◽  
Ray Method ◽  
Low Frequencies ◽  
High Frequencies ◽  
Beam Patterns

AbstractThe Five-hundred-metre Aperture Spherical Telescope (FAST) is being constructed in China. With an illuminated aperture of 300-m diameter, it will be the most sensitive single-dish radio telescope in the world. We calculate the beam patterns, gains, and efficiencies of the FAST at 200 MHz, 1.4 GHz, and 3 GHz. A program is developed to calculate the structural parameters and construct the FAST models. The three-dimensional beam patterns are calculated by utilising the shooting and bouncing ray method. We show that, with a coaxial horn feed, the FAST has a beam pattern of high gain and reasonably low first sidelobe over the frequency range of 200 MHz to 3 GHz. Compared with an ideal 300-m parabolic reflector, the un-illuminated spherical part of the FAST would make the power level near both sides of the main beam rise by at least 20 dB and the efficiency tends to decrease at high frequencies. At a zenith angle of 0°, its efficiencies at 200 MHz, 1.4 GHz, and 3 GHz are 71.72%, 66.94%, and 57.55%, respectively. We conclude that the FAST is an excellent telescope at low frequencies. At high frequencies, the triangular spherical panels and the gaps between panels are important factors that affect the performance of the FAST.

Receiving beam patterns in the horizontal plane of a harbor porpoise (Phocoena phocoena)

2005 ◽  
Vol 118 (2) ◽  
pp. 1172-1179 ◽  
Author(s):  
Ronald A. Kastelein ◽  
Mirjam Janssen ◽  
Willem C. Verboom ◽  
Dick de Haan
Keyword(s):  
Horizontal Plane ◽  
Phocoena Phocoena ◽  
Harbor Porpoise ◽  
Beam Patterns

A Beamformer to Play with Wall Reflections: The Icosahedral Loudspeaker

2017 ◽  
Vol 41 (3) ◽  
pp. 50-68 ◽  
Author(s):  
Franz Zotter ◽  
Markus Zaunschirm ◽  
Matthias Frank ◽  
Matthias Kronlachner
Keyword(s):  
Computer Music ◽  
Electroacoustic Music ◽  
Digital Audio ◽  
Sound Sources ◽  
Pierre Boulez ◽  
Acoustic Equations ◽  
Digital Audio Workstation ◽  
Beam Patterns ◽  
Auditory Objects

The quote from Pierre Boulez, given as an epigraph to this article, inspired French researchers to start developing technology for spherical loudspeaker arrays in the 1990s. The hope was to retain the naturalness of sound sources. Now, a few decades later, one might be able to show that even more can be done: In electroacoustic music, using the icosahedral loudspeaker array called IKO seems to enable spatial gestures that enrich alien sounds with a tangible acoustic naturalness. After a brief discussion of directivity-based composition in computer music, the first part of the article describes the technical background of the IKO, its usage in a digital audio workstation, and psychoacoustic evidence regarding the auditory objects the IKO produces. The second part deals with acoustic equations of spherical beamforming, how the IKO's loudspeakers are controlled correspondingly, how we deal with excursion limits, and the resulting beam patterns generated by the IKO.

The echolocation beam of bottlenose dolphins (Tursiops truncatus): High-resolution measurements of horizontal beam patterns and nearfield/farfield transitions

2016 ◽  
Vol 140 (4) ◽  
pp. 3131-3131
Author(s):  
Jason Mulsow ◽  
James J. Finneran ◽  
Brian K. Branstetter ◽  
Patrick W. Moore ◽  
Cameron Martin ◽  
...  
Keyword(s):  
High Resolution ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Horizontal Beam ◽  
Beam Patterns

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

Performance and applications of a field-emission gun TEM/STEM

1992 ◽  
Vol 50 (2) ◽  
pp. 942-943
Author(s):  
Judith M. Brock ◽  
Max T. Otten ◽  
Marc. J.C. de Jong
Keyword(s):  
Field Emission ◽  
High Resolution Imaging ◽  
High Quality ◽  
Small Energy ◽  
High Brightness ◽  
Small Probe ◽  
Resolution Imaging ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

A Field Emission Gun (FEG) on a TEM/STEM instrument provides a major improvement in performance relative to one equipped with a LaB6 emitter. The improvement is particularly notable for small-probe techniques: EDX and EELS microanalysis, convergent beam diffraction and scanning. The high brightness of the FEG (108 to 109 A/cm2srad), compared with that of LaB6 (∼106), makes it possible to achieve high probe currents (∼1 nA) in probes of about 1 nm, whilst the currents for similar probes with LaB6 are about 100 to 500x lower. Accordingly the small, high-intensity FEG probes make it possible, e.g., to analyse precipitates and monolayer amounts of segregation on grain boundaries in metals or ceramics (Fig. 1); obtain high-quality convergent beam patterns from heavily dislocated materials; reliably detect 1 nm immuno-gold labels in biological specimens; and perform EDX mapping at nm-scale resolution even in difficult specimens like biological tissue.The high brightness and small energy spread of the FEG also bring an advantage in high-resolution imaging by significantly improving both spatial and temporal coherence.

Structure Information From Electron Diffraction Intensities

1990 ◽  
Vol 48 (2) ◽  
pp. 516-517
Author(s):  
J. Gjønnes ◽  
N. Bøe ◽  
K. Gjønnes
Keyword(s):  
Computational Effort ◽  
Unit Cell ◽  
Small Unit ◽  
Structure Information ◽  
Dispersion Surface ◽  
Integrated Intensity ◽  
The One ◽  
Image Position ◽  
Convergent Beam ◽  
Beam Patterns

Structure information of high precision can be extracted from intentsity details in convergent beam patterns like the one reproduced in Fig 1. From low order reflections for small unit cell crystals,bonding charges, ionicities and atomic parameters can be derived, (Zuo, Spence and O’Keefe, 1988; Zuo, Spence and Høier 1989; Gjønnes, Matsuhata and Taftø, 1989) , but extension to larger unit cell ma seem difficult. The disks must then be reduced in order to avoid overlap calculations will become more complex and intensity features often less distinct Several avenues may be then explored: increased computational effort in order to handle the necessary many-parameter dynamical calculations; use of zone axis intensities at symmetry positions within the CBED disks, as in Figure 2 measurement of integrated intensity across K-line segments. In the last case measurable quantities which are well defined also from a theoretical viewpoint can be related to a two-beam like expression for the intensity profile:With as an effective Fourier potential equated to a gap at the dispersion surface, this intensity can be integrated across the line, with kinematical and dynamical limits proportional to and at low and high thickness respctively (Blackman, 1939).

convergent-beam diffraction from surfaces

1987 ◽  
Vol 45 ◽  
pp. 30-33
Author(s):  
J. A. Eades ◽  
A. E. Smith ◽  
D. F. Lynch
Keyword(s):  
Reciprocal Lattice ◽  
Three Dimensional ◽  
Grazing Incidence ◽  
Three Dimensions ◽  
Plane Figure ◽  
Transmission Electron ◽  
Convergent Beam ◽  
Beam Patterns ◽  
Beam Diffraction

It is quite simple (in the transmission electron microscope) to obtain convergent-beam patterns from the surface of a bulk crystal. The beam is focussed onto the surface at near grazing incidence (figure 1) and if the surface is flat the appropriate pattern is obtained in the diffraction plane (figure 2). Such patterns are potentially valuable for the characterization of surfaces just as normal convergent-beam patterns are valuable for the characterization of crystals.There are, however, several important ways in which reflection diffraction from surfaces differs from the more familiar electron diffraction in transmission.GeometryIn reflection diffraction, because of the surface, it is not possible to describe the specimen as periodic in three dimensions, nor is it possible to associate diffraction with a conventional three-dimensional reciprocal lattice.

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