Acoustics and Sound System for the Mainz Parliamentary Assembly Hall
The old Deutachhaus has been reconstructed and now houses the new Assembly Hall for the State Parliament of the Palatinate; it was completed in May, 1987. The The Assembly Hall can seat 100 members, 13 ministers, 20 executives, about 20 press members, and more than 100 visitors in the balcony. The acoustical design had to fulfill a high requirement for speech intelligibility of more than 5V=80% or AI=0.55 for the articulation index. Measurements and calculations after completion led to values of 5V=80% and AI=0.60 and RASTI=0.55 without and 0.63 with sound system out of 15 measuring spots in the Assembly Hall. The reverberation time was almost exactly achieved with an average value of 1.1 s between 63Hz to 8,000 Hz. The "aimed acoustics" represents an important principle for the acoustical design: the feedback of sound to the source is an acoustical response of the room. This is equal to a natural monitoring with a pleasant room impression. This applies for the speaker at the rostrum, for the chairman of the Parliamentary members at their seats. The sound system consists of 114 microphones (100 members, 13 ministers, and one for the chairman). The microphone selection panel is at the chairman's seat and is operated by him. The members are experienced in handling microphones and can adjust the sound levels appropriately. The sound system works with a feedback margin of around 10 dB. Feedback starts when about eight to ten microphones are opened simultaneously. In 1987, the author presented a paper in London which describes the many electronic features of the sound system and the first requirements for the acoustics. Now first experiences have confirmed that the acoustical conditions and the sound system are good; the statements of the users and the reaction of the press and public were very positive.
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