In the Trenches With CBS Sports During the Loudness Battle
By Dan Daley
At CBS Sports on Manhattan’s West 57th Street, the audio brain trust, led by Director of Engineering Bruce Goldfeder, is looking over graphs of NFL games. Three areas of measurement — dialog, effects, and the automated stereo downmix — are compared over about a 20-minute span of each game, including moments during which the home team scored.
“That way,” says Goldfeder, “you know you’re getting the game at one of its loudest points.”
The point of the effort, which is the latest part of a three-year program of overhauling the sports division’s audio, is to quantify a broadcast parameter that has been subjectively assessed more often than not: how loud is it, how loud should it be, and how loud should one sound element be in relation to another in the 5.1 age?
In a central control room, Goldfeder sits in the station he occupies during the NFL season. There, he has a Leitch routing switcher that can move him from game to game on multi-game day, as he monitors the mixes and gives feedback in real time to the mixers. The goal, he says, is to massage the mixes in the field and not have them processed at all during either the “back haul” from remote truck to control room or the “front haul” from control room to network distribution.
“We want it all to be exactly the same level from one game to the next and have it go from the mix to air with no adjustments at any point,” he says. “From console to home, only the [lead audio mixer] can adjust the levels.”
Goldfeder says the advent of multichannel broadcast audio put the loudness issue on the front burner. Even as the sound of the broadcasts continued to improve, the levels became less predictable, with differentials of as much as ±4 dB between games.
The keys to resolving that lie in a combination of the continued scrutiny of past mixes via graphical analysis and the further application of the ITU-R BS1770 algorithm, which is being implemented in various manufacturers’ hardware, such as Dolby’s LM-100 loudness meter, significantly increasing the precision level of loudness measurement.
“Dialog numbers are actually very consistent, from game to game and mixer to mixer,” says Greg Coppa, CBS Sports director of advanced technology and engineering, as he scrutinizes several weeks’ worth of graphs. “You start seeing the variation in the effects channels: as you see the levels of effects and dialog getting closer to each other, you encounter problems with intelligibility.”
They’ve found that the downmix channels have the greatest disparity, as much as ±4 dB between the loudest and the softest.
This number-crunching will ultimately create a baseline that all the broadcasts can work from. “The real trick is to apply uniformity to the mixes without taking away enough latitude on the part of the A1s to let them do the mix they want to do, the mix the game calls for,” says Coppa. “You want an exciting mix, but you don’t want disconcerting differences in levels between games.” And the team plans to achieve such a mix for the start of the 2009-10 NFL season. “Our goal is consistency in what we deliver to the consumer,” he says.
And what about the loudness of commercials versus the game audio? Coppa and Goldfeder exchange glances. “Commercials?” says Goldfeder with an arched eyebrow. “That’s another conversation.”