1342 Chapter 35
mental group in question.3,4 The electroacoustical trans-
ducers are positioned in the center of the group in
question according to the arrangement topography of
the orchestra, see the example in Fig. 35-3.
By evaluating the measured binaural room impulse
responses on the basis of the register balance measure-
(BR, see Section 7.2.2.15); it is possible to infer room-
acoustical measures for a required architectural modifi-
cation of the horizontal and vertical boundary surfaces
of the performance zone, and to clarify questions
concerning the vertical staggering of the orchestra. The
sound intensity-time behavior allows conclusions
regarding the sound attack of the individual instru-
mental groups, and regarding masking effects in the
frequency and time domains from which measures for
the acoustical formation of the secondary structure of
the room can be inferred.
Fig. 35-4A shows an example for the use of the
scaled-model measuring technique for a concert hall, as
compared to the original room, Fig. 35-4B.
35.1.2 Building a Computer Model, Entering Room
Data
Entering room data into a simulation program must be
simple and straightforward. A combination of graphical
and numerical entry of the data, planes, and vertex
points has to be supported. Entering the room into the
program must be efficient in order to make the program
work cost effective and intuitive. If the room entry takes
too long, the program becomes much less valuable as a
real design tool. There are different ways to enter room
data:
- By X, Y, Z coordinates.
- By text files.
- By import from professional drawing programs like
AutoCAD or SketchUp. - By use of drawing tools like prototypes or predefined
room shapes.
- By import from professional drawing programs like
Fig. 35-5A to D shows one example of a model with
different view options.
Simpler models that normally should have between
500 and a maximum of 1500 faces may be created
based on simple room shapes or prototypes. A manipu-
lation routine should allow one to stretch or shrink
dimensions to adapt the prototype to the requirements.
This way a simple room model for basic investigations
can be created within minutes.
Better would be the possibility of importing DWG or
DXF or other similar architecture files directly. But the
disadvantage here is that architects in the early design
phase do not create 3D models and offer only 2D draw-
ings. These drawings are of less use and so the acousti-
cian has to enter the model vertex by vertex, line by line
and area by area. Sometimes 3D models can be built by
expanding a 2D plan and by manipulating the result.Figure 35-3. Typical arrangement of simulated orchestra-
groups on a concert hall platform.
Wo BISt SBaFigure 35-4. Konzerthaus, Berlin.A. Acoustical indoor room model scale 1:20 with
simulated orchestra groups.B. Finished original room.