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account frequency dependent scattering. Only in special cases where the focus is on another frequency range, should this frequency be changed. Scatter coefficients > x.xx handled as uniform scatter From published material on measured scattering coefficients, there seems to be a general trend that modest scattering tends to be area based whereas high scattering is better represented by uniform scatter. In ODEON small scattering coefficients i.e. below x.xx is handled either with the Lambert Oblique or Lambert algorithms whereas scattering coefficients above x.xx are handled using uniform scattering. Scattering coefficients in the context above are the Reflection Based Scattering coefficients (if that option is activated); a typical result of this algorithm is that reflections close to an edge will be handled with uniform scattering which is desirable. Through empirical studies we have found that x.xx=0.5 yields best results. If using a value of 0 then all reflections are handled uniformly and if using a value of 1 then all reflections are handled using Lambert or Lambert Oblique as was the case in ODEON 8.0 and earlier. 8-89
9 Achieving good results The following section discusses how to obtain good results and indeed what is a good result. It is not a straight answer as to how the best result is obtained, merely a discussion that may provide some ideas as to what can be done in order to obtain reliable results in a program such as ODEON. The desirable precision - subjective limen Before discussing how to achieve good results, it is a good idea to outline just what a good result is. The subjective limen (or just noticeable difference - jnd) on room acoustical parameters should give a good suggestion as to the desirable precision. If the error between the ‘real’ (measured with some precision) and the simulated room acoustical parameter is less the one subjective limen, then there is no perceivable difference and the result is really as good as it can be, so it would be senseless to look for more precise results. In many cases it will be difficult or even impossible to obtain results at this precision and a poorer one will probably also be satisfactory for most purposes. Parameter Definition Subj. limen (ISO 3382-1, 2009) and (IEC 60268-16, 2003) for STI T 30 (s) Reverberation time, derived from –5 to – 35 dB of the decay 5 % rel. curve EDT (s) Early decay time, derived from 0 to – 10 dB of the decay curve 5 % rel. D 50 (%) Deutlichkeit (definition), early (0 - 50 ms) to total energy ratio 5 % abs. C 80 (dB) Clarity, early (0 – 80 ms) to late (80- ∞) energy ratio 1 dB abs. Ts [ms] Centre time, time of first moment of impulse response or 10 ms abs. gravity time G (dB) Sound level related to omni-directional free field radiation at 1 dB abs. 10 m distance LF (%) Early lateral (5 – 80 ms) energy ratio, cos 2 (lateral angle) 5 % abs. STI (RASTI) Speech Transmission Index 0.03 abs. Room acoustical parameters and their subjective limen as given by Bork (Bork, 2000) and Bradley (Bradley, 1986). Example 1: If the real G value is 1 dB and the simulated is 1.9 dB then the difference is not noticeable. Example 2: If the real LF value is 12 % and the simulated is 17 % the difference is just noticeable. Note! When comparing measured parameters to the ones simulated it should be kept in mind that the measured parameters are not necessarily the true ones as there are also uncertainties on the measured result. These errors are due to limited tolerances in the measuring equipment as well a limited precision in the algorithms used for deriving the parameters from the measured impulse response (or similar errors if results are not based on an impulse response measuring method). There may also be errors due to imprecise source and receiver positions. 9.1 Sources of error There are many sources of error in a room acoustical simulation, leading to results which are less than perfect (within one subjective limen). Sometimes this is quite acceptable because we are just interested in rough results, at other times we are interested in results as good as possible. In any case being aware of the sources of error may help getting the maximum out of ODEON. The sources of error (or at least some of them) are: The approximations made in the ODEON calculation algorithms. Inappropriate calculation parameters. Imprecise material absorption coefficients. Imprecise material scattering coefficients. 9-90
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ODEON ROOM ACOUSTICS SOFTWARE Versi
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ODEON Room Acoustics Software Versi
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Introduction This manual is intende
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SOFTWARE LICENSE AGREEMENT The foll
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Contents Introduction .............
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1 Installing and running the progra
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applied to all surfaces. In these c
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Update option Update to most recent
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2 Short guided tours This chapter w
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Define a line source (Combined edit
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Define a receiver grid and calculat
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Single Point response receiver and
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defined before ODEON can calculate
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Point Response calculations The Poi
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Archiving project files in one sing
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Define a multi surface source Click
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Other facilities in ODEON Apart fro
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2-34 Copenhagen Central Station Arr
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3 Modelling rooms Creating new room
Page 39 and 40: Experiences from tests with the fir
Page 41 and 42: 3.2.2 ODEON Extrusion Modeller A sm
Page 43 and 44: The drawing has now been scaled and
Page 45 and 46: By checking Move all layers on laye
Page 47 and 48: To rotate a surface around a point
Page 49 and 50: BLOCK’s are not supported ODEON c
Page 51 and 52: Geometric rules, glue surfaces Surf
Page 53 and 54: 3.4.1 Viewing the room in a 3DView
Page 55 and 56: Surfaces are missing from the model
Page 57 and 58: 4 Materials This chapter covers mat
Page 59 and 60: Another option is to change the abs
Page 61 and 62: utton for finding material in the l
Page 63 and 64: 5 Auralisation (Combined and Audito
Page 65 and 66: frequency response inverse to that
Page 67 and 68: are simulating an ordinary stereo s
Page 69 and 70: 6 Calculation Principles 6.1 Global
Page 71 and 72: The calculations carried out are di
Page 73 and 74: eflection order and up to the trans
Page 75 and 76: Scattering coefficient S s Surface
Page 77 and 78: oom; such as windows, doors, painti
Page 79 and 80: A last remark on Oblique Lambert is
Page 81 and 82: 6.9 Calculation method for Reflecto
Page 83 and 84: 7 Calculated Room Acoustical parame
Page 85 and 86: The calculated value of Lj(Average)
Page 87 and 88: 8 Calculation Parameters - Room Set
Page 89: Screen diffraction If this option i
Page 93 and 94: 9.1.3 Materials /absorption data Wr
Page 95 and 96: 10 Directivity patterns for point s
Page 97 and 98: inary and have the extension .SO8.
Page 99 and 100: An example; Full_Omni.dat on the fu
Page 101 and 102: 11 Line array sources This section
Page 103 and 104: 11.2 Playing with delay One advanta
Page 105 and 106: Figure 11-6. The radiation in octav
Page 107 and 108: Appendix A: References Affronides,
Page 109 and 110: Kristensen, J. (1984). Sound Absorp
Page 111 and 112: Appendix B: Vocabulary The techniqu
Page 113 and 114: Appendix C: Specify Transmission th
Page 115 and 116: Appendix D: Description of XML form
Page 117 and 118: Figure E3 Images of the Mono, Dipol
Page 119 and 120: When developing export facilities f
Page 121 and 122: InvertPhase="false" - If phase is i
Page 123 and 124: speaker deliver 1W. The reason why
Page 125 and 126: You may describe coordinates using
Page 127 and 128: Example 1: Const CeilingHeight 3.4
Page 129 and 130: As a special option for multi point
Page 131 and 132: 5411>5401 5512>5522 Elevation surfa
Page 133 and 134: If an elevation surface has 22 surf
Page 135 and 136: Name of counter to be used by the F
Page 137 and 138: The UCS command is used to create a
Page 139 and 140: As another option the colour of the
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Width is oriented in the Y-directio
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The Cone statement The Cone stateme
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### Const N 16 Const W 10 Const H 3
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Surf 2 ceiling 11 12 13 14 Surf 3 e
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Surf 100 Circular floor 100>100+N-1
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The window example shows how a cyli
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Appendix G: Importing geometries -
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