Working Group
1.73
Room Acoustics
Private studies
Practice shows a
multitude of difficulties to apply computer programs simulating room acoustic parameters
on any rooms. Not only the proper handling of programs is essential but also the
"correct" data input. Besides the geometrical room data that is above all the absorption grades a of room
limiting surfaces and its scattering coefficient s.
Working group 1.73 made it its business
to give defined calculation possibilities on room simulation programs to users and
developers. This way they can check their own calculation results. As starting base for a
simple reference model a room with seven surfaces will be given. The room and its
dimensions is equivalent to the PTB studio neglecting all
designing details.
Both the adoption of room coordinates and the calculation of room acoustic
parameters according to ISO 3382 can be carried out with most room simulation programs.
This is intended as base model to check the functions and use of room simulation programs.
The 9 known room acoustic parameters T30, EDT, C80,
D50, TS, G, LF, LFC and IACC
are suggested to be calculated for comparison in 6 octave bands with normal conditions. The results are to be listed in an EXCEL-table that can be downloaded here.
At first walls have uniform absorption
properties to allow for a simple calculation and a reduction of errors. The room
coordinates and the sources (S1,S2) and receivers (R1,R2,R3) inside the room you can find here. Likewise you can find the results of a "correct" simulation to allow a
comparison between actual and rated values to simplify the trouble search.
Everbody interested can do calculations for
himself or he can also take part in a round robin and that way make his results available
to an international comparison. You just have to send us a completed EXCEL-file by email.
Of course your results remain confidential! If interested please get information at "round robin".
Furthermore it is possible to download
a single impulse response to calculate the most important
parameters according to ISO 3382. The results can be compared to those of round robin 2.
Do your own calculations on ELMIA hall
(Round Robin II):
We offer the computer models of ELMIA
hall in different formats: CATT, ODEON, DXF(a new PTB version more exact than the Round
Robin version), EASE and as Excel file. All versions are geometrically equivalent. Go to
the download page and get your favourite model for doing the
calculations and compare it with the results of the
participants of Round Robin II.
Special test
signals for evaluation
For testing the evaluation software for
decay time and other parameters which only need a single impulse response, we created a
wave file containing exponentially decaying sine components
(multisine) at all centre frequencies of the 3rd octave bands: at 50 Hz..10000 Hz. If you
use this file (16 bit mono, 44,1 kHz) for evaluation of T30, a frequency independent value of 2.0 seconds should be indicated. Otherwise
check your evaluation. At the beginning 150ms silence is inserted for checking the signal
onset detection. The peak level is 100% (normalized).
Further decaying noise signals are
available for testing more natural conditions. A white noise
and a pink noise of 2.5 s decaying with a reverberation
time of 2.0 seconds. The difference of white and pink noise will be obvious evaluating the
G values (in dB), because the power per constant bandwidth is different for
white(constant) and pinknoise (decreasing) . Note that for the two random signals the
evaluation contains a high degree of uncertainty in contrast to the deterministic
multisine signal. This effect has been investigated by generating 5 pink noise signals and
calculating the mean values and their standard deviation of the evaluated data. Find the
results in an Excel file for 7 room acoustic
parameters. The shown data were calculated using the aurora software by A. Farina ( http://www.ramsete.com/).
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