Sound is what separates a true cinema experience from simply watching TV. A dedicated and fully engineered room with effortless dynamics, pumping bass and fully immersive surround sound is a visceral, emotional experience. These qualities which make the experience are also the biggest challenge in cinema design – delivering the experience only to those in the cinema and nowhere else.
There are two distinct elements to optimising cinema acoustic to ensure that the maximum performance can be delivered regardless of the choice of speaker system; Acoustic Treatment and Sound Isolation. The improvements provided by each system can be complementary but by taking a dedicated approach to each, the best results can be achieved. In this article we will focus only on Sound Isolation.
Sound Isolation relates to the construction of the acoustic shell to maximise the attenuation between the cinema and surrounding spaces. We can tackle sound isolation by applying MAID – Mass, Air permeability, Isolation and Damping.
In Sound Isolation, it is important to dispel one myth at the earliest stage. Attenuating the level of sound transfer to a suitable level is our goal – completely preventing the leakage of sound from a high performance cinema is simply not possible making the choice of location very important. This difficulty is most apparent in bass notes which have a long wavelength that is extremely difficult to contain.
Luckily for us, human hearing is much less sensitive to low frequency sounds and this is reflected in the standards used to describe the spectra of noise and in the assessment of isolation performance.
It is convenient to use single numbers to explain performance but in sound that can only ever be a starting point to the overall system design. Understanding noise and isolation ratings is an article all of its own however!