The conventional movie theater is giving way to a huge mall, with plenty of retail outlets, and the top floors of such places are usually dedicated to a number of small halls replacing the conventional movie theater experience. The large theater had a very different acoustical characteristic and these small halls require a fairly different approach for acoustical treatment.
I’ve worked on the PVR malls at Orion mall, and now at the Vega Mall, and some issues seem to be common across both projects. Let’s begin by looking at common acoustical issues at the smaller halls. (The larger halls are vanishing, and those that are remaining, can be treated similar to large auditoria – coming up in a different post!)
This requires maximum consideration. The biggest problems I see frequently are noise coming in from the food courts, gyms sharing walls and floors, air-conditioning chillers on top of the building, and noise from adjoining halls, in some cases! Thankfully, with most of these being located on the higher floors, traffic noise is never an issue. But I know one place where the door to one such hall was separated from the external facade by 6 feet of corridor space, and the glazing was insufficient to contain noise from airplanes passing by!
This is what most people think acoustical treatment is all about. Yes, these spaces need to be optimized for clear speech, as well as music, and of course, deep bass. I’ve watched movies in some really dead sounding spaces. The speech sounded great, but the songs, the accident, all sounded very superfluous. It didn’t help that the movie was a crashing bore.
While we’re discussing wall treatment, no, absorptive materials on the wall will NOT prevent transmission of sound. Care must be taken to check sound transmission between walls of adjoining halls, and then design acoustical treatment required.
This is the other most commonly seen issue. The hall sizes are large enough to allow plenty of LF in the room, but it is a task to ensure they’re sufficiently diffuse, and it is essential to ensure that room resonances don’t unnaturally colour the sound. There are 5D movie theaters coming up these days! It’ll be a lovely to write a separate blog post on them, some day soon.
Actually, the line-of-sight accuracy is all taken care of by the architects, and if the raking is correct and the headrest is not too high, one can ensure there’s good amount of direct sound reaching each row. But we’re more interested in the seating in terms of upholstery. Usually, these places are carpeted, and the seating provides a GOOD amount of absorption. It’s so significant, that the treatment on the walls must be carefully calculated to ensure that the space doesn’t sound dead after the furniture is moved in.
The coverage of the speakers must be plotted to ensure that no place is receiving more than the intended amount of sound. The front seats have it the worst usually. Using logarithmically curved line array speakers can help, but care needs to be taken to add the right number of speakers in each array, else the sound becomes too directional.
Now here’s the other thing about audio. You DON’T NEED to hear it that loud. And if you’re a regular with movies in such places, I strongly advise you to carry a pair of earplugs. Choose how deeply you want to plug them in, and you will hear everything – the HF, the LF, the mids. Just not as loudly as intended. Honestly – I’ve always been most comfortable sitting through a movie when I have my ears plugged. I’ve attended a healthy amount of concerts, and have always maintained comfortable loudness levels by using earplugs. Sounds absurd? I know. Please heed my advise. I speak out of collected experience and foresight. You don’t want to be speaking these words someday, out of bad experience.
Now there are plenty of other parameters we acoustical engineers calculate, to ensure the right balance of sound, etc. But these spaces lie between glorified home theaters and large auditoria. The importance for each parameter is therefore, determined by the size of each hall.
These spaces are leading to even more novel concepts – a person I know has turned a space into a home theater area. He has a few rooms, and each room is a dedicated home theater. Groups of friends, or family can book a room all for themselves, food is catered, and you can watch a movie with first class acoustics and audio, with only your loved ones! The acoustical challenge is to ensure that there is sufficient isolation between rooms, and of course, to even out the bass response in small rooms. There’s just so much happening on the audio/video front in Bangalore alone! Interesting times ahead!