This work provides a systematic experimental evaluation of the impact of scattering on sound field diffusivity in a proportionate medium-small sized room. A scale model is set up in many ways by increasing the amount of scattering, and detailing measurements of the reverberation time in each case. With the aid of statistical tools, the role of scattering in the process of achieving a diffuse sound field from initially non-diffuse conditions is outlined and a set of reference scattering threshold values is derived. It is found that the same values ensure the validity of the Sabine formula when corrections are adopted in its application. Reverberation time is also predicted in non-diffuse conditions by the Nilsson approach, and its performance is systematically compared with measurements. The Nilsson method was a better predictor of reverberation time under non-diffuse conditions than classical reverberation time formulas. However, for diffuse sound fields, the same method tended to diverge from measured values. An application using more realistic room conditions is developed together with computer simulations. The results outline that there is limited benefit to using computer-aided design models instead of simple formulas to predict reverberation time for non-diffuse sound fields in proportionate medium-small sized rooms.

1.
EN12354-6:2003
,
Building Acoustics—Estimation of Acoustics Performance of Buildings from the Performance of Elements. Part 6: Sound Absorption on Enclosed Spaces
[
European Committee for Standardization (CEN)
,
Brussels
,
2003
].
2.
T. J.
Cox
and
P.
D’Antonio
,
Acoustics Absorbers and Diffusers
, 1st ed. (
Spon
,
London
,
2004
), pp.
87
127
and 335–352.
3.
T. J.
Cox
,
B.-I.
Dalenback
,
P.
D’Antonio
,
J. J.
Embrecths
,
J. Y.
Jeon
,
E.
Mommertz
,
M.
Vorländer
, “
A tutorial on scattering and diffusion coefficients for room acoustics surfaces
,”
Acta Acust. Acust.
92
(
1
),
1
15
(
2006
).
4.
M.
Hodgson
, “
Evidence of diffuse surface reflections in rooms
,”
J. Acoust. Soc. Am.
89
(
2
),
765
771
(
1991
).
5.
Y. M.
Lam
, “
The dependence of diffusion parameters in a room acoustics prediction model on auditorium sizes and shapes
,”
J. Acoust. Soc. Am.
100
(
4
),
2193
2203
(
1996
).
6.
Y. M.
Lam
, “
A comparison of three diffuse reflection modeling methods used in room acoustics computer models
,”
J. Acoust. Soc. Am.
100
(
4
),
2181
2192
(
1996
).
7.
Y.
Yasuda
,
A.
Ushiyama
,
S.
Sakamoto
, and
H.
Tachibana
, “
Experimental and numerical studies on reverberation characteristics in a rectangular room with unevenly distributed absorbers
,”
Acoust. Sci. Technol.
27
(
6
),
366
374
(
2006
).
8.
T.
Hanyu
, “
A theoretical framework for qualitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls
,”
J. Acoust. Soc. Am.
128
(
3
),
1140
1148
(
2010
).
9.
H.
Kuttruff
,
Room Acoustics
, 4th ed. (
Spon
,
London
,
2000
), pp.
124
268
119
and
137
141
.
10.
J. L.
Davy
,
I. P.
Dunn
, and
P.
Dubout
, “
The variance of decay rated in reverberation rooms
,”
Acustica
43
,
12
25
(
1979
).
11.
J. L.
Davy
, “
The variance of impulse decays
,”
Acustica
44
,
51
56
(
1980
).
12.
M.
Hodgson
, “
On the prediction of sound fields in large empty rooms
,”
J. Acoust. Soc. Am.
84
(
1
),
253
261
(
1988
).
13.
ISO354:2003
,
Acoustics—Measurement of Sound Absorption in a Reverberation Room
(
International Organization for Standardization
,
Geneva, Switzerland
,
2003
).
14.
ISO17497-1:2004
,
Acoustics—Measurement of the Sound Scattering Properties of Surfaces—Part 1: Measurement of the Random-Incidence Scattering Coefficient in a Reverberation Room
(
International Organization for Standardization
,
Geneva, Switzerland
,
2004
).
15.
E.
Nilsson
, “
Decay processes in rooms with non-diffuse sound fields. Part 1: Ceiling treatment with absorbing material
,”
Build. Acoust.
11
,
39
60
(
2004
).
16.
E.
Nilsson
, “
Decay processes in rooms with non-diffuse sound fields. Part 2: Effect of irregularities
,”
Build. Acoust.
11
,
133
144
(
2004
).
17.
E.
Gerretsen
, “
Estimation methods for sound levels and reverberation time in a room with irregular shape or absorption distribution
,”
Acta Acust. Acust.
92
,
797
806
(
2006
).
18.
M.
Kylliäinen
,
E.
Nilsson
, and
P.
Chigot
, “
Effectiveness of EN12354-6 and other calculation methods of room acoustics in ensuring required acoustic conditions in typical enclosed spaces
,” in
Proceedings of Euronoise2006
,
Tampere
,
Finland
(
2006
), Paper
201
.
19.
E.
Nilsson
and
N.
Andersson
, “
Sound decay and steady-state level in rooms with ceiling treatment
,” in
Proceedings of International Symposium on Room Acoustics: ISRA2007
,
Sevilla
,
Spain
(
2007
), Paper
S14
.
20.
T. E.
Bartel
and
E. B.
Magrab
, “
Studies on the spatial variation of decaying sound fields
,”
J. Acoust. Soc. Am.
63
,
1841
1850
(
1978
).
21.
M. R.
Schroeder
, “
Effect of frequency and space averaging on the transmission responses of multimode media
,”
J. Acoust. Soc. Am.
46
,
277
283
(
1969
).
22.
D.
Lubman
, “
Precision of reverberant sound power measurements
,”
J. Acoust. Soc. Am.
56
,
523
533
(
1974
).
23.
J. S.
Bradley
, “
Predicting theatre chair absorption from reverberation chamber measurements
,”
J. Acoust. Soc. Am.
91
(
3
),
1514
1524
(
1992
).
24.
J. S.
Bradley
, “
Reply to: ‘Comments on “Predicting theatre chair absorption from reverberation chamber measurement” ’ [J. Acoust. Soc. Am. 93, 2238–2240 1157 (1993)]
,”
J. Acoust. Soc. Am.
95
(
2
),
1155
1157
(
1994
).
25.
ISO3382-2:2008
,
Acoustics—Measurement of Room Acoustic Parameters-Part 2: Reverberation Time in Ordinary Room
(
International Organization for Standardization
,
Geneva, Switzerland
,
2008
).
26.
H.
Arau-Puchades
, “
An improved reverberation formula
,”
Acta Acust. Acust.
65
(
4
),
163
180
(
1988
).
27.
S.
Chiles
and
M.
Barron
, “
Sound level distribution and scatter in proportionate spaces
,”
J. Acoust. Soc. Am.
116
(
3
),
1585
1595
(
2004
).
28.
A.
Astolfi
,
V.
Corrado
, and
A.
Griginis
, “
Comparison between measured and calculated parameters for the acoustical characterization of small classrooms
,”
Appl. Acoust.
69
(
11
),
966
976
(
2008
).
29.
S. R.
Bistafa
and
J. S.
Bradley
, “
Predicting reverberation times in a simulated classroom
,”
J. Acoust. Soc. Am.
108
(
4
),
1721
1731
(
2000
).
30.
E.
Nilsson
, “
Room acoustics measures for classrooms
,” in
Proceedings of Internoise2010
,
Lisbon
,
Portugal
(
2010
), Paper
631
.
31.
Odeon 10.1®, www.odeon.dk (for details on algorithm and significance of setup parameters; last viewed 9/13/2012).
32.
M.
Hodgson
and
R.
Orlowski
, “
Acoustics scale modelling of factories, Part II: 1:50 scale model investigations of factory sound fields
,”
J. Sound. Vib.
113
(
2
),
257
271
(
1987
).
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