Playback Visits Audyssey and the USC Immersive Audio Lab

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Playback Visits Audyssey and the USC Immersive Audio Lab

Last week I had the opportunity to visit Audyssey Laboratories, Inc. in Los Angeles, CA, for a wide-ranging press briefing, which included a tour of USC’s Immersive Audio Laboratory (the very laboratory in which many of the core technologies behind Audyssey’s room EQ system were first developed). I had known about the USC Immersive Audio Lab ever since I was first introduced to Audyssey a number of years back, but last week was my first chance to see it up close.  As a home theater enthusiast and as an audiophile, I must admit that I just plain like the idea that there is a well-equipped and well-funded lab at a major American university that is dedicated—give or take a bit—to researching and to improving the overall quality of the surround-sound experience.

History

USC’s Immersive Audio Lab was founded in 1996 after two professors, Tomlinson Holman (Film Sound, and the man whose initials contributed the “TH” in THX) and Chris Kyriakakis (Electrical Engineering), applied for and won an NSF grant to create the lab.  The lab also receives some support from the Defense Department/U.S. Army, whose interests—in case you are wondering—involve development of highly realistic training simulations that have immersive, 3D soundtracks.

Purpose

From the outset, the lab focused on studies of the complex interaction between listeners, room acoustics and reproduced sound, with an eye toward seeing how audio signal processing might overcome acoustics problems and improve the overall surround-sound experience. What is distinctive about the approach taken at USC is that it marries several different but related research disciplines:

1.  Physical Acoustics (how sounds behave within enclosed spaces)

2.  Psychoacoustics (how we perceive both real and reproduced sounds)

3.  Film Sound (how we produce multi-channel recordings/soundtracks—and the technical standards behind them—to create believable, enveloping, immersive audio environments)

4.  Audio Signal Processing (how we apply advanced digital signal processing techniques to identify and correct room acoustic problems, and manipulate audio signals to improve perceived sound quality)

Some of the lab’s research focused on attempts to model, duplicate, and—if possible—to improve upon the elaborate manual set-up procedures (which, in my view, are part science and part art) that Tomlinson Holman used in developing custom equalization settings for surround-sound systems in upscale movie theaters. In a conversation I had with Holman about a year and a half ago, Holman told me that at first his manual processes could always beat the best EQ algorithms the USC lab developed. Over time, though, the lab’s algorithms became increasingly sophisticated (eventually using fuzzy logic to calculate necessary DSP-driven adjustments in both time and frequency domains for each channel in the system), so that the lab’s EQ results eventually equaled and then surpassed Holman’s expert manual EQ process. The automated EQ system developed in the USC lab was licensed by Audyssey in 2002 and has since gone on to become the Audyssey MultEQ ™ automated room/speaker EQ system that is featured in many of the higher performance AVRs and A/V controllers now on the market.

The USC Immersive Audio Lab, also known as an “ERC” (Engineering Research Center) of the NSF and as the USC IMSC (Integrated Media Systems Center), is an impressive facility. The lab consists of two listening rooms (one larger, one mid-sized), plus an elaborate equipped electronics room. The larger listening room was purpose-built for the lab and is the quietest room on the USC campus (carrying an NC10 rating). The space features room-within-room construction, a free-floating floor that is supported from below by a grid of damped isolation jacks, 14’ ceilings (so researchers can experiment with speaker placement well above ear-level), and special, sealed acoustic isolation doors (which cost $10k apiece and look like they came off the Starship Enterprise).

Audyssey DSX Demo and Overview

During my time at the USC lab, I was treated to a demonstration of Audyssey’s newest technology: an up to 10.2-channel surround system known as DSX (Dynamic Surround Expansion). DSX is a complex enough system that I plan to devote a separate blog to the topic next week. But for now, here are the basics.

DSX uses DSP technology to create expansion channels that augment the usual 5.1-channels found in most surround soundtracks (and multichannel music recordings). The additional expansion channels serve two purpose: first, they fill in perceived gaps to the left and right sides of the surround soundstage, and second, they convey height information that helps make the soundstage feel more like a 3D hemisphere of sound rather than a relatively flat circle of sound that presents lateral sound information only.

DSX Channel Scheme

When the full-on DSX surround-sound scheme is implemented, up to 10.2 channels can be used, as follows:

Channel 1: Left Main (placed 30 degrees to the left of the system centerline, at ear level)

Channel 2: (NEW) Left Height (placed 45 degrees to the left of the center line, and at a 45 degree up-angle relative to ear level)

Channel 3: (NEW) Left Wide (placed 60 degrees to the left of the center line, at ear level)

Channel 4: Left Surround (placed 120 degrees to the left of the system centerline, at or above ear level)

Channel 5: Center Front (placed on the system centerline, front of room, as close to ear level as practicable)

Channel 6: (NEW, Optional) Center Rear (placed on the system centerline, rear of room, at or above ear level)

Channel 7: Right Main (placed 30 degrees to the right of the system centerline, at ear level)

Channel 8: (NEW) Right Height (placed 45 degrees to the right of the center line, and at a 45 degree up angle relative to ear level)

Channel 9: (NEW) Right wide (placed 60 degrees to the right of the center line, at ear level)

Channel 10: Right surround (placed 120 degrees to the left of the system centerline, at or above ear level)

The “.2” Channels: Subwoofer 1 and 2 (positioned for best in-room bass response, but typically might be positioned in left/right front or left/right side locations)

Next week, we’ll talk about Audyssey’s DSX technology in greater depth. 

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