Experimental Recording Technologies Spice Home Entertainment 2001
No one who has heard the Super Audio Compact Disc—either two-channel or multi-channel—would disagree. DVD-Audio, the putative competitor for your high-resolution dollars, hasn't had quite the auspicious debut that SACD has enjoyed, but plenty of engineers are working to exploit its potential.
One is Mark Waldrep, PhD, of AIX Media Group, a West Hollywood, CA–based DVD startup. At AIX's booth in the Analog Ballroom, Waldrep, a trained musician, composer, and electrical engineer, is demonstrating a DVD recording technique that allows the listener to vary his apparent position and angle to a working orchestra with just a push on the button of his remote control. Waldrep makes the magic happen with a 24-microphone array mixed down to eight tracks, and says it might even be possible to synchonize it with its video equivalent, so that one day music fans watching a recorded opera might be able to move in for a visual and sonic close-up during an aria. Waldrep reveals his audiophile roots when he admits that he prefers DVD-A with the visuals shut off. "Not enough processing power for all that input," he joked.
Another fascinating experimental technology is Perceptual Soundfield Reconstruction, developed at AT&T Labs by James Johnston, a psychoacoustics expert who contributed substantially to the development of Advanced Audio Coding and MPEG-2 Audio-AAC. At the heart of Perceptual Soundfield Reconstruction, which was developed by AT&T engineers, is a seven-channel array of microphones—five of them hypercardiods positioned at 72 degree increments in a horizontal circle, one shotgun mic pointed directly overhead, and one shotgun pointed directly at the floor.
The horizontal mics have a 3dB drop-off relative to each of their neighbors, and are spaced in a circle that approximates the diameter of a human head. The upward-pointing vertical mic captures vertical cues, and the downward-pointing one picks up floor reflections, which yield cues as to the dimensions of the acoustic space, explained Schuyler Quackenbush, a principal technical staff member at AT&T's digital signal processing research lab.
Quackenbush, who is also chairperson of the IEEE Technical Committee on Audio and Electroacoustics, said the seven-channel recording technique is compatible with all five-channel surround technologies. The signals recorded from the vertical mics can be blended into the lateral playback channels in such a way as to add a substantial degree of realism to surround sound. Quackenbush backed up his claims with demonstrations of the same recordings played in stereo and in full-surround modes. Mixing down seven channels to five is a relatively easy process, according to Johnston. The demonstrations were offered privately to journalists on the first day of HE 2001, but will be open to the public on Saturday and Sunday.
Headroom's irrepressible Tyll Hertsens has made good on his promise to create a headphone bazaar here at the New York Hilton. Fully half the available real estate in the Analog Ballroom is devoted to Headroom's display, where show-goers may audition virtually every type of headphone and headphone amplifier available—including what Hertsens claims is the world's only fully balanced headphone amp (actually a pair "strapped" for balanced operation) driving a pair of upper-end Sennheisers with a custom-made cable.
Make that two for me and none for you: this Web-fingered reporter was the only competitor all day to win the "Crappy Headphone Toss," wherein those of us strolling the audiophile midway were invited to test our skill in a headphone version of the carnival ring toss game. My prize: a pair of Etymotic "ear buds," which ought to work just fine when I'm watching DVD movies on my new Sony Vaio laptop. Tyll, by the way, has abandoned the business suit he sported at CES in Las Vegas and has returned to his signature Hawaiian shirts. He can always be counted on to inject much-needed levity into these sometimes dour affairs. Why other folks don't enjoy their business the way he does remains a mystery. Music IS all about enjoyment, isn't it?