PROGRAMM - DAGA 2012

170 DAGA 2012 ProgrammMi. 14:50 chromium 2.02 Virtuelle Akustik 2Map projections for the graphical representation of spherical measurementdataB. BernschützFachhochschule Köln - Institut für NachrichtentechnikMany tasks in acoustics and audio entail capturing spatial measurementdata on a sphere and require an appropriate graphical representationof the data. For a circular dataset the polar plot is a very popular diagramtype. The corresponding diagram type for a spherical dataset isa three-dimensional balloon plot. However, the latter requires a threedimensionalillustration to present the full dataset simultaneously. Actualscreens and print media typically only represent two dimensions.The balloon must be rotated or be printed in different angles in orderto achieve an overview of a full dataset. A very similar problem arisesin cartography where e.g. the spherical earth surface must be reducedto two-dimensional plane maps. This problem engaged cartographers,geographers and mathematicians for centuries and a large set of differentmap projections has been developed. Some of the proposals arevery convenient to the problem of three-dimensional measurement datarepresentation. Different projection types and their suitability to the presentedproblem are discussed. The projections can be applied to anykind of spherical measurement data. In acoustics it can be helpful fordata visualization in sound field analysis or e.g. to illustrate radiationpattern of instruments and loudspeakers.Mi. 15:15 chromium 2.02 Virtuelle Akustik 2A new omni-directional source based on a ring radiatorR. Kruse a ,A.Häußler b und S. van de Par ba TU Braunschweig; b Universität Oldenburg, Institut für Physik - AkustikIn this contribution a new omni-directional source is presented that isring radiator like. The ring radiator is created by mounting the front oftwo dynamic loudspeakers opposite to one another and by closing ofthe rear sides of the loudspeakers with a quasi-conical closure. In thisway a small volume of air is enclosed between the two cones whichcan irradiate sound symmetrical along the circular ring that separatesthem. Measurements show that the radiation pattern is rather directionindependent up to frequencies of about 10 kHz for a cone diameter of6.5 cm. As should be expected, the radiation pattern does not depend on(horizontal) rotations around the (vertical) symmetry axis going throughthe centers of the loudspeakers. Interestingly, (vertical) rotations towardsthe symmetry axis show only small variations of the sound pressure levelof on average 2 dB and maximal 7 dB. The new omni-source is rathersuitable for the measurement of room impulse responses because: 1)the direct sound path is hardly influenced by the chosen horizontal angle,2) the spectral coloration is hardly dependent on angle leading to a veryuniform excitation of the reverberant sound field.