Hybrid Products Integrate Loudness Management With Surround Processing

By Dan Daley

Like almost everything that gets digitized, surround processing is melding with other processing, notably with loudness management. This convergence makes particular sense: the issues of apparent loudness that have plagued mono and then stereo are exacerbated in a multichannel environment.

The result is a growing number of hybrid products that incorporate surround management with up/downmixing and loudness measurement and control technology from partnering companies. An example is Harris’s UpMix, which incorporates DTS Neural’s multimerge technology and can upmix and manage a 5.1 mix over a stereo transmission. Harris is migrating the technology from single-rack outboard units to embedding it in their conversion and frame-synch technology.

“There is more overlap now between loudness and surround from an operational point of view,” says Randy Conrod, digital products manager for Harris. “The disparity between stereo and 5.1 sound has exacerbated the problem in surround. You have to address the loudness issue for all of them as close to the point of origin as possible, not by putting a leveling box at the end of the [broadcast] chain.” Hence, integrating a loudness-management function that can anticipate how a multimerge function will manage and mix an upmixed stereo-to-5.1 conversion offers more than a fighting chance to control the loudness of the brachiated mix.

For Jim (JJ) Johnston, chief scientist at DTS Neural, this kind of systems integration is a no-brainer — precisely because the ultimate target of the broadcast is the brain, where the head-related transfer function (HRTF) demands that loudness be adjusted for the skull’s topography.

“The front, side, and back of the head all perceive level differently,” he explains. “The side shoots sound directly into the ear, with a big peak in the ear canal; the front of the head tends to be rather neutral in its processing; but the back, where the pinna shading is, essentially acts like a low-pass filter. Doing a loudness calculation without integrating the surround processing [including equalization and panning] isn’t going to work because you have to know how everything is related to the HRTF. You have to know the directionality of the incident sound in order to anticipate the loudness.”

On a less neurological, more visceral level, Linear Acoustic President Tim Carroll says the idea for his company’s Aero QC product, which combines loudness management with 5.1 management and other functions, came from its experience at the 2008 Olympics in Beijing.

“I was watching the mixers looking constantly at a number of different displays, to the point where I thought they were going to get whiplash,” he recalls, adding that the next generation of products reflect that epiphany. “It’s coincidental that the focus shift from level to loudness came about at the same time we’re making the transition to digital and 5.1, but that’s actually working out for the best since we can combine those functions now.”