Home Engineering Building Acoustics
The cinema industry has standards that are applicable (e.g., [2, 3]).
In the olden days, the sound insulation requirements with regard to the outside were not that high, as there were no sound systems save for the ubiquitous piano. Gradually, sound systems were introduced and the frequency domain of interest was steadily enlarged. To give an idea of this evolution, in the 1970s the sound insulation of cinemas used to be evaluated with a 90 dB(C) pink noise emitted in a theatre, while the sound level in the neighboring projection halls should not exceed 35 dB(A) and NR30. Nowadays, this evaluation is performed with a 105 dB(C) pink noise emitted in a projection hall, while the sound level in the neighboring projection halls should not exceed 32 dB(A) and NC27. More to the point, some special effects are sometimes required. The film Earthquake introduced spectators and neighbors alike to new sensations in the low-frequency range.
Therefore, the fundamental questions will be: What would the end user like to do, and what will the project actually allow him to enjoy (e.g., regular cinema projection, surround, or even Omnimax projections)?
Now let’s consider the internal acoustics of the cinema projection hall: With reference to the idea that one must be able to perceive the sound as coming from the place on the screen where the action occurs, this means that acoustic reflections must be avoided. This in turn means that absorptive treatment should be applied on the walls and ceiling.
The sound levels generated by mechanical equipment should not be a hindrance. This typically means a background noise level value in the 30 to 35 dB(A) range, together with a frequency limit contour (e.g., NC) according to the standards in force.
|< Prev||CONTENTS||Next >|