This column was reprinted with permission from InfoComm and originally appeared here.
Until the 1980s, cinemas were an acoustical hodge-podge, with dimensions of varying sizes and speakers arrayed in ways that often blasted sound at those in front and challenged those in the rear to hear. Then, in 1977, came Star Wars, George Lucas’ paean to the sci-fi serials of the1930s and 1940s. Its audio was anything but FDR-radio-address quality.
After putting that much effort into the sound of the first two Star Wars films, Lucas realized he had to raise the playback experience substantially in the cinema environment itself. Thus was born THX, named for its prime developer, Tomlinson Holman, Lucasfilm’s resident audio wizard. The “X” stood for crossover, a way of segmenting audio frequency bands into appropriate banks of speakers and amplifiers, such as subwoofers, part of the THX standard that would revolutionize how we experienced film sound.
THX, introduced in 1983 for Return of the Jedi, was seminal: As theaters became better environments in which to listen to film sound, it prompted Hollywood to put more effort into movie soundtracks. Moreover, the concept of an improved listening space also migrated to other environments, creating an entire new industry around home theaters. But among the biggest collateral beneficiaries were spaces intended for live events. Concerts, theatrical productions, and performing arts centers — even churches and shopping malls — benefitted from enhanced awareness of issues such as acoustics, matching between speakers and amplifiers, and other specifications outlined by THX.
And that’s largely where things have stood ever since. In the 30 years since THX’s standards changed cinema sound, those protocols, which addressed issues such as standing waves created by parallel theater walls and the addition of a center channel for dialog, have remained largely static, even as the technology around them, from ray-tracing measurement technology for highly steerable line array speaker systems, has reached new levels of sophistication and capability. A consortium of technology organizations, led by the Society of Motion Picture and Television Engineers (SMPTE) and supported by InfoComm International, the Audio Engineering Society (AES) and the Acoustical Society of America (ASA), has set out to update the standards we use to create optimal listening environments.
Strengthening the B-Chain
In the beginning, SMPTE’s Theater B-Chain Study Group, formed in 2010, focused on cinema environments and centered its work on what’s known as the B-chain: the type and positioning of elements such as speakers, amplifiers and processors that comprise the part of a cinema sound system that audiences experience. (The A-Chain is made up of components such as the cinema server, projector, audio router and other similar systems.) The SMPTE study group set out to see how technologies, techniques and products developed over the last three decades could better measure and perform across the B chain to create a better-sounding environment.
The study group’s findings were then handed over to a standards group, a technology team dubbed TC-25CSS (Technology Committee 25, Cinema Sound Systems), announced on March 4, 2013 to “update SMPTE standards and recommended practices to address opportunities created by the many technical advances since standards last were created, as well as to improve the quality and consistency of cinema sound,” according to a SMPTE statement. The committee, led by Brian Vessa, executive director of digital audio mastering at Sony Pictures Entertainment, has 130 members, representing more than 90 companies and academic institutions from 14 countries.
TC-25CSS, which is the first such committee dedicated solely to cinema sound, aims to standardize techniques and tools for optimizing sound systems and cinema acoustics. Current activities include development of a recommended practice for measurement and calibration of B-chain sound systems using modern standards and measurement technology; creation of a standard pink-noise test signal that works for a digital environment; a final report on data and findings from the Theater B-Chain Study Group; and work by two new study groups examining immersive audio systems and new electroacoustic measurement methods and target curves.
It’s a complex undertaking (the cinema sound lexicon now includes immersive formats such as Auro-3D, Dolby’s ATMOS, IOSONO and Sonic Tier), but one that promises to extend its benefits well beyond movie houses.
Joe Bocchiaro, CTS-D, CTS-I, InfoComm’s Vice President of Standards and Industry Innovations, says that while cinemas and live-performance spaces tended to move along separate development tracks in recent decades, a study that InfoComm conducted three years ago underscored how the cinema audio environment diverged from evolutions in live sound and digital distribution. It also illuminated the shared interests between SMPTE and InfoComm constituencies today. InfoComm focused on the experience of simulcast concerts and other events held in movie theaters. Bocchiaro cited one Foo Fighters simulcast concert, in particular, that drew complaints based on poor sound quality in the cinemas. This laid the foundation for the collaboration now in place.
“Everyone has a stake in this,” Bocchiaro says. The challenges include the fact that despite advances in precision measurement ability, audio analysis remains heavily weighted toward subjective interpretation, which can be addressed by more rigorous and widely accepted measurement standards and by the refinement (or elimination) of putative nostrums of questionable validity. Most notable of these is the X Curve, a high-frequency roll-off beginning at 2 kHz at -3 dB/octave, then -6 dB/octave from 10 kHz. It was based on pink-noise measurements of typical cinemas taken three decades ago. Critics contend that for contemporary cinemas, the X Curve is irrelevant, or worse, that its application can actually make cinema spaces sound less intelligible. In fact, a redefinition of pink noise for the digital era is part of what SMPTE is seeking to accomplish with the TC-25CSS initiative.
Since 2011, InfoComm has been working on a suite of standards addressing four distinct areas of sonic concern in enclosed spaces: spectral balance, undesirable sound, reproduced speech and music quality, and sound pressure level optimization in audiovisual systems. Combined with InfoComm’s 2009 ANSI standard, Audio Coverage Uniformity in Enclosed Listener Areas [PDF], the suite [PDF] is meant to offer a comprehensive characterization of a sound system. Compliance with the parameters defined in all the standards would, for the first time, make it possible — in a measureable, reproducible way — to ensure that a sound system provides audio of high quality, intelligibility and fidelity.
InfoComm’s goals happened to intersect nicely with those of SMPTE. Bocchiaro says InfoComm suggested that the organizations harmonize their efforts to create a set of standards that apply to a wide range of enclosed performance spaces, from cinemas to performing arts centers.
“With representatives from all of these organizations working together, we have a technical dream team that’s not duplicating each other’s efforts,” he says.
While SMPTE members continue to focus on the cinema B-chain, and InfoComm pursues its audio standards suite, the two other professional organizations have carved out their own niches. AES has staked out two areas, both focused on measurement. TheAES-X218 project will review the parameters that affect the audience experience in rooms, as well as the objective measurement methods necessary to quantify them. This effort should provide a basis for more detailed standardization of measurement and calibration protocols for controllable parameters. AES-X219 will indentify a standard method of measuring frequency and impulse response for sound systems in auditoriums.
The ASA is looking at how to apply findings from its own research and that of the other groups to create a set of standards for education environments, such as classrooms and lecture halls, to improve the intelligibility of life-safety systems, like those required by NFPA 72.
There’s still a long way to go, both in terms of time and depth, for all of these pieces to come together. The TC-25CSS group was formed in March, and it faces many months of work before clear standards emerge. “We’re at the beginning of a huge adventure,” asBocchiaro puts it. But the benefits for sound in all kinds of enclosed spaces will make the journey worthwhile.