Loudness Report, Part Two: In the Trenches
By Dan Daley
SVG Audio Editor
The debate over consistent loudness levels not only from one channel to the next but within a single channel’s programming stream continues to have different networks taking different approaches. And it also seems to be an issue undergoing constant revisions in those approaches.
Bruce Goldfeder, CBS Sports director of engineering, says addressing level consistency is an ongoing process, one in which promulgating a cognizance of levels and manual monitoring of incoming audio from numerous remotes on major game days has heightened awareness of the issue throughout the department. This year, he says, he intends to create a more uniform philosophy throughout the division regarding such specifics as microphone choice and placement as part of an evolving “best practices” protocol.
On the technology side, he says, CBS Sports will likely integrate Dolby’s LM100 loudness meter to provide more objectivity in what is a highly subjective proposition.
“I’d like to have that added to the remotes so that the operators can monitor dialog level in a consistent manner,” he explains. “You can establish certain parameters, like, say, setting peaks at -14 [dB], but that’s always going to be subject to interpretation by the mixer. Some will view that conservatively while others will continue to push it up.”
Consistency, he stresses, needs to start in the back halls, prior to integration with commercials and interstitials. Level disparities between program and commercial audio tend to be the area that draws most of the consumer criticism for audio.
In the production trucks at sporting events, mixes are being intently scrutinized for level disparity, and mixers develop their own measures in response. Kevin Cleary, senior technical audio producer for ESPN Event Operations and mixer for two of broadcast’s loudest events, the X Games and NASCAR, says that, ultimately, sound is a perceptual proposition as far as the viewer is concerned.
“You can measure SPL and other parameters, but, in the end, it is a subjective situation,” he says. “Compression can help smooth out overall volume, but volume is only one part of the what’s being called the loudness debate.”
Most of the technology tools being used in broadcast to address loudness are not found at the field level, in remote trucks. Cleary suggests that a useful rule of thumb in the mixing trenches is to keep a 3- to 6-dB degree of separation between announcers’ audio and all other audio elements in a 5.1 mix.
“The idea of finding one ‘key’ as a solution is illusive,” he says. “The solution is going to be a combination of technology and techniques taking place at all points along the signal path.”
Jim Starzynski, principal engineer and audio architect for NBCU advanced engineering at NBC Universal, concurs that loudness issues in the digital era require a strategic response: “For proper level-matching between programming, commercials, and other DTV stations, it’s critical that each network has a plan to manage their loudness overall.”
NBCU’s loudness strategy is primarily procedural, and Starzynski says that the network has no plans to add external, conventional dynamic-range-control processing to its network audio.
“NBCU requires our mix engineers match a companywide loudness standard of -23 LKFS,” he explains. “We have the -23 dialnorm metadata encoded at our stations for transmission to the audience’s receivers. With this performed correctly, sports programming will match other NBCU shows in loudness and the majority of commercials, promos, and channel changes, as well.”
Surround mixes are of particular interest in this context. “Surround mixing must be carefully monitored by the mix engineer to make certain loud dramatic crowd effects never drown out the announcers,” Starzynski says. “We encounter this possibility frequently with sports production and ask our engineers to carefully monitor the mix to make certain dialog intelligibility is never compromised.”
NBCU recommends the use of a loudness meter in clear sight at the mix position that is measuring all channels of the audio in real time. “With this available,” Starzynski says, “our engineers can easily set average loudness, manage dynamics, and confirm that show audio and commercials will transition properly. This technique is simple and very effective.”
But he and other audio supervisors agree that consistency has to go beyond individual networks to be truly effective. “After 10 years of ATSC broadcasting, there still are many stations that don’t practice ATSC DTV loudness,” Starzynski says. “This causes wide variation among station audio in a market and, at times, misleads the audience to think that louder is better. Because ATSC uses dialnorm and its signal attenuation to match levels, properly set stations may sound softer than those not operating at the correct ATSC level. This is one of the greatest problems we have faced in the transition.”
For Part One on Loudness, go to www.sportsvideo.org/portal/artman/publish/article_14181.shtml.