b'Construction briefing675The auditoriums height will be chosen by the design team to obtain the appropriate volume of 30000 m 3 . The ceiling Acoustic diffusion will havewill not necessarily be flat. It The subjective parameterto be generated by roughnessis understood and considered of acoustic power is related toon the reflective surfaces in theacceptable that the total height the objective strength criterionroomto multiply the number(omitting the acoustic reflectors) G. For the Paris auditorium, theof acoustic reflections and breakabove the stage can be greater mean value of G (calculatedthe mirror effect of too smooththan 20 m.over a set of representativeor too large reflecting surfaces. seats which excludes the seatsAs an example, an importantIt is required that one or located within 5 m from thediffusion can be obtainedmore reflectors are placed stage) must be between +3 dBthrough convex surfaces thatabove the stage to generate and +6 dB. The spatial variationsspread acoustic reflections on areflections that facilitate the of the loudness G in the room,wider area than plan surfaces. listening conditions amongstexcluding the seats within 5mthe musicians.from the stage, must be lessReflective surfaces: 1400 m2 than 3 dB with respect to theincluding 500 m2 close to theSelection of requirements.mean over the entire room musicians (less than 15 m from aSource: Kahle Acoustics and (3 dB). point of the stage). Altia (2006), Acoustic brief.69 Photo: Lida Guan'