The calculation methods for handling of scattering has been greatly improved in version 8 of the ODEON program. Two new techniques (described below) have been implemented in order to increase the accuracy of the predictions provided by Odeon. The methods improves quality of results without any substantial increase in calculation time and at the same time it has been made easier to select realistic scattering properties for the surfaces. The mew methods are the Reflection Based Scattering method and Oblique Lambert. For details about these algorithms, please refer to the Odeon manual or the paper and presentation below.
|Paper - Forum Acousticum - 2005||Presentation - Forum Acousticum 2005|
The Reflection Based Scattering method is in short a method which calculates a scattering coefficient that is unique to each reflection. This coefficient includes diffraction phenomenon based on:
It is no longer needed to specify different scattering coefficients for surfaces with the same material in order to take into account the size or location of a surface - indeed Odeon will do a better job. Even though only one scattering coefficient is entered for each surface, this coefficient is expanded to cover the hole frequency range, using typical frequency functions for scattering coefficients.
Oblique Lambert is a technique which allows for inclusion of frequency depending scattering in the late reflection method of Odeon. Depending on the scattering coefficient the area radiation provided by late secondary sources is tilted towards the specular direction. If the calculated scattering coefficient is zero the secondary source will point in the specular direction and if it is one then it will point in the normal direction of the surfaces as a traditional Lambert source. Because this technique will make part of the Oblique Lambert source point out of the room, a compensation factor to is applied in order to avoid energy loss. The factor depends on tilting angle, it is 1 for 0 degrees and 2 for 90 degrees.
Odeon 8.0 includes support for the Common Loudspeaker Format. The Common Loudspeaker Format is an open format which is a supported by several loudspeaker manufactures as well as developers of room acoustical programs and /or programs for investigation of loudspeaker coverage. A free viewer which allows detailed viewing of data contained in Common Loudspeaker Format files can be downloaded at www.clfgroup.org where additional information can also be found about the group currently supporting the format etc.
It is not strictly required that the CLFViewer is installed in order to use directivity files stored in the CF1 (octave, 10 degrees data) resolution and CF2 (1/3 octave, 5 degrees data) formats, however we do recommend that you do download and install the CLFViewer if you wish to use CLF files as the viewer is capable of displaying full directivity balloons as well as additional information such as impedance and 6dB widths. If a directivity pattern is available from the loudspeaker manufacturer in the CLF1 as well as in the CLF2 format, then only the CLF2 files having the highest angular resolution should be installed - the 1/3 octave resolution will not be used, ODEON will rather translate the balloons into octave band balloons compatible with the energy based calculation methods applied by ODEON. In order to install new directivity files in the CLF format, simply extract /copy the files to your ODEON directivity file directory e.g. C:\Odeon 8.0 Combined\DirFiles\ If data for a loudspeaker is not available in any of the CLF formats you may encourage the loudspeaker manufacturer to make it available in the format; all the tools needed in order to create and verify directivity data in the Common Loudspeaker Format is available at www.clfgroup.org.
The Odeon Extrusion Modeler has been released in version 2 and has been greatly improved on a number of points. With the current release a room such as the one above can be modeled within minutes. Version 2 supports:
Support for PolyFace entities makes it easier to import geometries sucessfully without having to step trough multiple conversion processes.
Improved support for the 'oldfashined' Polyline which is used for modeling in of complex shaped surfaces in some CAD programs - such as Rhino
CAD entities which must be converted inside the CAD program before exported to ODEON are reported when encounted by Odeon when attempting to import a DXF file - allowing proper action to be taken.
Balls which are lost through holes in the geometry are now being visualized making the tool a valuable tool when checking geometries.
It is possible only to visualize reflections which are reflected by selected surfaces - the same surfaces as used for 3D Reflector coverage
The Alfa graph, a graph showing the absorption properties of the materials used in the current room has been added to Quick Estimate, so including these data in the report is just a click away
The reflection density graph has been added to the Single point response results. The reflection density display is the experts utility which can be useful for investigation of the errors with the geometry, quality of a calculation as well problems with the room.A vertical ruler added to 3DView's when the projection is turned off (shortcut P) A DC filter has been applied to the auralization ensuring that calculated BRIR's that there is no DC offset in the BRIR's used for binaural auralization. The DC filter can be selected from the Auralization setup dialog.