ACOUSTICS [Film Technology]

acoustics 
[Film Technology]

Acoustics (Greek, akouein, “to hear”), term sometimes used for the science of sound in general. It is more commonly used for the special branch of that science, architectural acoustics, that deals with the construction of enclosed areas so as to enhance the hearing of speech or music. The acoustics of buildings was an undeveloped aspect of the study of sound until comparatively recent times. The Roman architect Marcus Pollio, who lived during the 1st century BC, made some pertinent observations on the subject and some astute guesses concerning reverberation and sound interference. The scientific aspects of this subject, however, were first thoroughly treated by the American physicist Joseph Henry in 1856 and more fully developed by the American physicist Wallace Sabine in 1900. Acoustics (theatre), the science of sound as applied to theatrical performance. The astonishingly good acoustics of Greek amphitheatres such as that at Epidaurus were developed by trial and error rather than detailed knowledge of physics and mathematics. Indeed, the history of the application of mathematics to the analysis of sound in an enclosed room is less than a century old. The Boston Symphony Hall, built in 1901, was the first auditorium to benefit from the analysis of acoustics by Wallace Clement Sabine. Sabine pointed out that the limited range of the spoken voice, compared to music, may explain in part why theatre has been relatively ignored by acousticians, compared to concert halls. The lack of attention paid to acoustic design and analysis of the theatre is also due to the history and tradition of theatre building which, provided the rules were followed, invariably ensured a successful natural acoustic. Sabine formulated a key equation in acoustics that calculates the reverberation time of an enclosure in the 1920s. Since then, there have been enormous developments in acoustic theory, analysis, and measurement. The study of room acoustics is now a complex, highly mathematical subject. Nevertheless, the essential requirement is simple: that the choice of reverberation time should be carefully selected to suit the intended uses of the auditorium. Theatrical production has special requirements in terms of acoustics. Unlike a seated orchestra, actors move about a wide area, often speaking with their back to the listener. There are also a number of sources of background sound that need to be controlled, in addition to ensuring that the speech on stage is clearly audible—the noise of modern and sophisticated lighting systems and mechanical plant, for example.Modern theatres are invariably expected to be “multi-purpose auditoria”, and have to accommodate anything from wrestling and string quartets to rock music, making the specification of a single, optimum set of acoustic requirements difficult. Another problem is size. Because of their large proportions, these new auditoria rely on sound reinforcement systems. These have evolved from the “assisted resonance” system developed by Peter Parkin and used to good effect in London's Royal Festival Hall in the 1960s. The challenge of the future lies in the possibility of using electro-acoustic reinforcement systems. The use of these remains controversial amongst actors and musicians, but suitably subtle systems may prove to be acceptable to all. 

ACOUSTIC RESONANCE 

Can occur as the sound reverberates [reverberation] to and fro between parallel non-absorbent surfaces. Acoustic resonance can be avoided by sound diffusion. This is usually achieved by introducing deliberate irregularities in the surfaces involved. 



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