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Comparisons between Computer Simulations of Room

Acoustical Parameters and those Measured in Concert

Halls

Jens Holger Rin de1*, Hiroyoshi Shioka wa **,

Claus Lynge Christensen** andAnders Christian Gade**

*Norwegian Institute of Building Research,

P.O. Box 123 Blindern, N-0314 Oslo, Norway

**Department ofAcoustic Technology,Building 352,

Technical University ofDenmark, DK-2800 Lyngby, Denmark

Summary: A number of European concert halls were surveyed in 1989 [l]. In this paper

comparisons are made between measured room acoustical parameters and those obtained from

computer simulations using the ODEON pmgram version 3.1 on two concert halls. One is

Musikverein in Vienna and the other is Concertgebouw in Amsterdam. Comparisons are also made

between the results obtained from computer simulations using models with high geometrical fidelity

and those from models with simplifications to geometry on both concert halls.

Geometrical

Data from Computer Simulations

Two models of each concert hall are used for computer simulation. One is made

with high geometrical fidelity (C.H.) and the other one is made with

simplifications to geometry, mainly in the platform area (C.S.). The latter is in

better agreement with the laws of high frequency modeling.

Two models of Musikverein in Vienna are shown in Fig.1 and 2. Those of

Concertgebouw in Amsterdam are shown in Fig.3 and 4.

Source and receiver positions in simulation models are defined according to

survey in 1989. Sx (01-3) are source positions. Px are measureing position of

early decay time on the platform for each source position. All Sx and Px positions

are one meter above the floor. Rx (ml-5 or 6) are receiver positions in audience

area. All Rx positions are 1.2 meters above the floor.

1) Musikverein in Vienna (Actual Volume : 15000 m’)

a) C.H. model: Number of surfaces in room is 110.

The estimated volume is 15113 m’.

b) C.S. model: Number of surfaces in room is 64.

The estimated volume is 16048 m’.

Fig.1 C.H. model of Musikeverein

Fig.2 C.S. model of Musikverein

2) Concertgebouw in Amsterdam (Actual Volume : 18700 ti)

a) C.H. model: The number of surfaces in room is 84.

The estimated volume is 19923 m’.

b) C.S. model: The number of surfaces in room is 62.

The estimated volume is 20072 m’.

Fig.3 C.H. model of Concertgebouw

Fig.4 C.S. model of Concertgebouw

Acoustical

Parameters

Reverberation time(RT): Comparisons of measured(M) and calculated RT on

the receiver position R2 in middle of audience area in the stalls and R4 in

audience area of a balcony when the source position is S 1 (typical soloist position)

are shown in Fig.5, Fig.6 (Musikverein) , Fig.7 and Fig.8 (Concertgebouw).

Three series of RT are displayed in each of the Fig.5-8; measured RT in 1989[1]

and calculated RT by computer simulations using models of C.H. and C.S..

All three series of RT are similar except RT at 125Hz of Fig.5.

1.51

, ,

125

250

500

125

250

500

Frequency

[Hz]

Frequency[Hz]

Fig.5 RT in Musikverein (Sl-R2)

Fig.6 RT in Musikverein (Sl-R4)

3.5

--CM

-*--CH.

--A--

C.S.

125

250

500

125

250

500

Freq”ency[Hz]

Frequency[Hz]

Fig.7 RT in Concertgebow(Sl-R2)

Fig.8 RT in Concertgebouw(Sl-R4)

Early decay time(EDT) on the platform: Comparisons of three EDT on the

receiver position P2 (07 : middle of left side strings between first and second

violins) when the source position is S2(middle of right side strings between violas

and cellos) are shown in Fig.9 and Fig.10. Acording to Fig.9, EDT of C.S. is in

better agreement with that of M than that of C.H. in Musikverein. Acording to

Fig.10, the difference between the two sets of calculated data is small and they

are similar to the measured data except at 2kHz in Concertgebouw.

250

500

250

500

Frequency[Hz]

Fig.9 EDT on the platform in Musikverein

Fig. 10EDT on the platform in Concertgebouw

Level (L) and Clarity (C): Comparisons of L and C on the receiver position R2 and

R4 in Musikverein when the source position is Sl are shown in Fig.11 and 12

Differences in Level between M and C.S. are less than about 2dB. Differences in

Clarity between M and C.S. are large in R2 but small in R4 from 250Hz to 4kHz.

125

250

500

125

250

500

Frequency[Hz]

Frequency

[Hz]

Fig. 11 Level in Musikverein

Fig. 12 Clarity in Musikverein

Accuracy rating of acoustical parameters: The average of all resulting

relative errors for each acoustical parameter between M and C.H. ,C.S. at 500Hz

are shown Fig.13 and 14 (Subjective limen: 5% for RT and EDT, 1dB for L, 0.5dB

for C, 1Oms for Tq0.06 for LF[2]). Relative Errors of EDT and C are large in both

concert halls. Relative errors of C.H. are smaller than those of C.S. except RT in

Musikverein but both of them in Concertgebouw are similar except RT.

EDT

LEF

EDT

LEF

Acoustical

parameters

Acoustical

parameters

Fig. 13 Relative errors in units of

Fig.14 Relative errors in units of

subjective Iimen in Musikverein

subjective limen in Concertgebouw

Conclusion

* Measured and calculated reverberation times in single positions are in good

agreement.

- Models with simplifications to the geometry are more useful than those with

high geometrical fidelity for EDT on the platform.

. In both halls the average relative errors of Level and LEF are small(l-2 sub.

limen) and those of

Clarity are large(4-6 sub. limen).

References

111A.C.Gade: Acoustical Sowey of Eleven European Concert Halls. DTU Report No.44. 1989

121 Michael Vorlander: International RoundRobin on Room Acoustical ComputerSimulations,l5th

International

Congress of Acoustics,1995

Rindel - Comparisons between Computer Simulations of Room.pdf

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