Home Engineering Building Acoustics
The technical area of a cinema can easily be sizable: There usually is one air handling unit (AHU) per room (as one does not want to lose the whole facility in case of a technical problem) plus one for the hall, one for the restaurant, and smaller units for the cold rooms of the restaurant and the sweet corner. While most of this equipment will stop after the operating hours, the cold room equipment will carry on. One must appropriately dimension the radiated sound power level of the equipment (including the relevant silencers and noise barriers).
Some facilities feature a small dwelling for the head operator or the director. While this individual will be awake during the operational hours of his facility, his family might not be. Therefore, it is highly necessary to provide some serious sound insulation (at least 65 dB) with regard to the activities in the facility.
Surround and Omnimax
The ultimate aim of the cinema as it is nowadays is to try to blend the optical image with the acoustical image. To achieve such a feast, there are a few techniques involved.
The oldest one had the projection performed on a hemicylindrical or even hemispherical screen. That screen was made of perforated metal, and the loudspeakers and HVAC terminals were hidden behind the screen . Due to economics, the outer shell containing the facility usually was either a cylinder or a sphere, with corresponding risks of focusing that were solved through lots of absorptive materials (1 m thick is not uncommon for such purposes) located between the projection screen and the outer shell.
More recently some existing projection theatres have been outfitted with a surround system featuring loudspeakers on the lateral walls, back wall, and also ceiling . In order to avoid creating a salient in the sight of the audience, recesses are needed in the ceiling, and this may seriously complicate matters with regard to sound insulation between projection theatres.
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