145Chapter 7
Acoustics for Auditoriums and
Concert Halls
by Dr. Wolfgang Ahnert and Hans-Peter Tennhardt
7.1 Introduction............................................................................. 147
7.2 Room-Acoustical Criteria, Requirements...................................................... 147
7.2.1 Time Criteria......................................................................... 148
7.2.1.1 Reverberation Time RT60....................................................................................... 148
7.2.1.2 Bass Ratio (BR) (Beranek).......................................................... 151
7.2.2 Energy Criteria....................................................................... 152
7.2.2.1 Strength Measure (G) (P. Lehmann)................................................... 153
7.2.2.2 Sound Pressure Distribution (' L)..................................................... 153
7.2.2.3 Interaural Cross-Correlation Coefficient (IACC)......................................... 153
7.2.2.4 Center Time (ts) (Kürer)............................................................ 154
7.2.2.5 Echo Criterion (EK) (Dietsch)........................................................ 154
7.2.2.6 Definition Measure C 50 for Speech (Ahnert)............................................. 154
7.2.2.7 Speech Transmission Index (STI) (Houtgast, Steeneken)................................... 155
7.2.2.8 Articulation Loss, Alcons, with Speech (Peutz, Klein)..................................... 156
7.2.2.9 Subjective Intelligibility Tests........................................................ 156
7.2.2.10 Clarity Measure (C80) for Music (Abdel Alim)......................................... 159
7.2.2.11 Sound Coloration Measures (KT) and (KH) for Music (Schmidt)........................... 160
7.2.2.12 Spatial Impression Measure (R) for Music (U. Lehmann)................................. 160
7.2.2.13 Lateral Efficiency (LE) for Music (Jordan), (LF) (Barron) and (LFC) (Kleiner)................ 161
7.2.2.14 Reverberance Measure (H) (Beranek)................................................. 161
7.2.2.15 Register Balance Measure (BR) (Tennhardt)........................................... 162
7.3 Planning Fundamentals.................................................................... 162
7.3.1 Introduction.......................................................................... 162
7.3.2 Structuring the Room Acoustic Planning Work.............................................. 164
7.3.2.1 General Structure.................................................................. 164
7.3.2.2 Room Form and Sound Form........................................................ 165
7.3.3 Primary Structure of Rooms............................................................. 165
7.3.3.1 Volume of the Room............................................................... 165
7.3.3.2 Room Shape...................................................................... 167
7.3.3.2.1 Ground Plan........................................................................ 168
7.3.3.2.2 Ceiling............................................................................ 171
7.3.3.2.3 Balconies, Galleries, Circles........................................................... 173
7.3.3.3 Room Topography................................................................. 173
7.3.3.3.1 Sloping of Tiers, Sight Lines........................................................... 173
7.3.3.3.2 Platform Configuration in Concert Halls.................................................. 175
7.3.3.3.3 Orchestra Pit........................................................................ 177