The surround ensemble of loudspeakers, if properly specified, can easily produce a sound
field that is uniform throughout the back two-thirds of the house, and level variations can often be held
within a range of 2 to 3
Details of surround system specification will be covered in a later section.
When all of the above points are properly addressed, the sound in a cinema can approach that
which we take for granted in a post-production screening facility which is, after all, how the picture
director intended it to sound. It is only when such details as these have been carefully worked out that
the effects intended by the sound mixer can be appreciated by the viewing audience.
CONSIDERATIONS
A. Noise Criterion (NC) Requirements
The usual sources of noise in a cinema, outside of the patrons themselves, are air handling
and transmission of noise from the outside. In the case of multiplex installations, there can be leakage
from adjacent cinemas as well. Not much can be done about a noisy audience, but it is true that at the
mixing engineers take into account certain masking noise levels which may be
encountered in the
and even do the final mix under simulated noisy conditions (4).
Figure 9. Noise Criterion (NC)
band
Figure 10. Sound Transmission Curves
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