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A FEW BASIC RULES
As with any project, a cinema or theatre project starts with a program: What does the end user (and the payer too!) actually want (e.g., which capacity, which activities, what interactions with the immediate environment?)? This means the various requirements must be identified and the relevant acoustic objectives stated. In today’s spirit of sustainable development, one must be conscious that a team effort (i.e., architects, structural engineers, HVAC, and acoustics, just to name a few) occurs and make sure that the various solutions that are considered at the design stage are compatible with each other. Acoustics often is part of a global problem that can only be solved by a complete design team fed the relevant data by the end user.
In the olden days the projection booth featured a regular cinema projector and all the mechanical equipment needed to store the assembled film roll and pass it through the projector. This meant that enough space had to be allocated for all this equipment. In addition to the clicking sounds of the film rolling, there was the purr from the exhaust fan cooling down the projector. In order to reduce the amount of light emitted by the projection booth into the projection theatre, there usually was only a small openable aperture with a thick glazing for the operator to check the correct situation in the theatre, and a small aperture with a high-quality glazing for the projector. Due to the fire constraints (implying that the glazing and frame assembly had been subjected to a fire test) and the optical constraints (implying that the image would suffer no distortion), one typically was left with an 8 to 10 mm thick special glazing.
By the way, the facility always had an operator whose task was to prepare and assemble the rolls of films, and if need be, repair quickly the film roll in case of breakage.
Good news: Nowadays, numeric projection no longer requires a real operator, and one does not need to worry about the noise of this individual or the mechanical noise from the projector. Now for the bad news: It has become fashionable to show to the audience the modern projection equipment, so a large projection window is now used. However, due to the significant noise from the projector (whose exhaust is much more powerful than before), better sound insulation is needed between the projection booth and the projection room. This usually leads to a double projection glazing, with the outer glazing inclined for both acoustic and optical purposes.
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