AN INVESTIGATION INTO THE ACOUSTIC EFFECT OF
CINEMA SCREENS ON LOUDSPEAKER PERFORMANCE
Philip Newell
Jana Guijarro García
Keith Holland
1 ABSTRACT
Acoustics consultant, Moaña, Spain (philiprnewell@gmail.com)
ISVR, University of Southampton, UK (janaguijarro@gmail.com)
ISVR, University of Southampton, UK (krh@isvr.soton.ac.uk)
The advent of digital soundtracks for cinema has brought about the possibility of significant improvements in the quality of sound in cinemas. One aspect of this sound quality involves the transmission of sound through the screens, behind which the loudspeakers are almost invariably placed. The acoustic properties of the various different types of screen are currently not completely understood, and very limited data on this subject is available from the screen manufacturers. Although a number of published studies have already been undertaken relating to the acoustic performance of screens, some have had commercial interests involved, and some of the contrasting results that have been presented have not been from tests conducted under similar circumstances. This paper is concerned with investigating the acoustic properties of three different screens through detailed measurements, all carried out under the same conditions in an anechoic chamber.
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6 CONCLUSIONS
What is very clear from these tests is that there are multiple factors affecting the way in which a cinema screen interacts with a loudspeaker. When many things are changing at once, each component of any aspect of the response can mask the effects other changes. It has proved to be very difficult to tell from visual inspection of the plots, either in isolation or in groups, precisely which mounting angles or distances could definitively be stated to be most desirable from a sound-quality point of view.
It is evident that the woven screens out-perform the mini-perforated screen acoustically, but as explained in Section 2 there are situations where the latter have overriding advantages from an optical point of view or where great size is required.
Before any reliable recommendations can be made about precisely how best a screen should be mounted for optimal sound transmission, even from this limited series of tests, auralisations would be required, based on the convolution of the measured impulse responses with a representative selection of cinema soundtracks. Actual listening tests in realistic environments would be very difficult to realize in practice. Long time-intervals between tests would perhaps be unavoidable, and room acoustics would add a further complication. However, such tests may ultimately prove to be necessary.
The ‘best distances’ between the screen and the loudspeaker may depend on the screen type and the loudspeaker mounting arrangements (flush-mounted in an absorbent-covered wall; free- standing; backs to a solid wall in an untreated cavity; backs to a wall in an absorbent-filled cavity; etc.). Even the size of the loudspeaker cabinet in all but the flush-mounted situations will have a bearing on the quantity of reflexions and the areas of the screens over which they will spread.
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What is very clear from these tests is that there are multiple factors affecting the way in which a cinema screen interacts with a loudspeaker. When many things are changing at once, each component of any aspect of the response can mask the effects other changes. It has proved to be very difficult to tell from visual inspection of the plots, either in isolation or in groups, precisely which mounting angles or distances could definitively be stated to be most desirable from a sound-quality point of view.
It is evident that the woven screens out-perform the mini-perforated screen acoustically, but as explained in Section 2 there are situations where the latter have overriding advantages from an optical point of view or where great size is required.
Before any reliable recommendations can be made about precisely how best a screen should be mounted for optimal sound transmission, even from this limited series of tests, auralisations would be required, based on the convolution of the measured impulse responses with a representative selection of cinema soundtracks. Actual listening tests in realistic environments would be very difficult to realize in practice. Long time-intervals between tests would perhaps be unavoidable, and room acoustics would add a further complication. However, such tests may ultimately prove to be necessary.
The ‘best distances’ between the screen and the loudspeaker may depend on the screen type and the loudspeaker mounting arrangements (flush-mounted in an absorbent-covered wall; free- standing; backs to a solid wall in an untreated cavity; backs to a wall in an absorbent-filled cavity; etc.). Even the size of the loudspeaker cabinet in all but the flush-mounted situations will have a bearing on the quantity of reflexions and the areas of the screens over which they will spread.
Register today to download the complete and full report.
