Surround Sound

Recommended Reading: 3D Sound Overview

3D Audio Overview PDFA long time ago, when I was still in school in Toronto, I became fascinated with an obscure form of surround sound recording known as Ambisonics. In researching a paper for school I became smitten by the approach conceived by English mathematician Michael Gerzon. It’s a truly elegant system, something beyond the commercially successful surround sound approaches that we all know.

I was especially impressed with the Cowboys Junkies 1988 album, The Trinity Session. It was recorded in a old church on King Street in Toronto, in a single day. The band played in this place with incredible acoustics, ringed around a single Calrec Soundfield microphone. The Soundfield microphone is the surround microphone design based upon the theory originally published by Michael Gerzon at Oxford University.

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Binaural Fun With AmbiExplorer For Android

AmbiExplorer_framedMy issue with use of the term 3D with reference to binaural voice conferencing service stems from the fact that I’ve been having some fun with real 3D audio over the past couple of months. This has come about since Hector Centeno released AmbiExplorer for Android, an application that lets us decode Ambisonic recordings for binaural playback in headphones.

AmbiExplorer plays back first-order B format files as well as UHJ encoded stereo files. As opposed to simply left, center, right, etc. a B format file is actually comprised of four channels known as W, X, Y & Z. These correspond to three directional signals and an omnidirectional reference signal.

By performing some matrix math on these signal in a coordinated fashion the entirety of the soundstage can be transformed in 3D space. AmbiExplorer decodes the four signals into a binaural feed, allowing the user to rotate their listening perspective in real-time. You can think of it as a 3-axis “balance” control.

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This is the sort of “3D” that I will not up with put!

3DRemember the opening sequence Sesame Street? Well, this post is brought to you by the number 3 and the letter D…cuz some of you weren’t paying attention all those years ago!

Both Voxeet and Dolby Voice are interesting binaural conference services. However, some of the marketecture being deployed sets off alarm bells in my mind. Despite claims to the contrary, and the echo of such claims by the media, I don’t believe that what they offer is “3D audio.”

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Immersive Audio: Sound All Around You

Ok, this is me diving into the deep-end of something that very possibly literally no-one in the world cares about. That’s just so typical of me. Actually, I know that a few people are starting to clue in about this because I’ve heard it come up here and there in conversation, most recently at the Sept 15th HDComms event in NYC.

This post is actually the third in a series. In the first (Pink Floyd: The Making Of Money & Directionality) I took a quick look at pop music recording practices and specifically the practice of recording things “close-mic’d” the adding ambience through synthetic means. In the second in the series (Codecs, Wideband & Stereo: A Conversation At Amoocon) I followed a conversation in the hallway at AMOOCON 2009, noting aspects of the discussion pertaining to “stereo” or the conveyance of directionality.

Once we get beyond PSTN audio quality, when wideband is accepted as normal, then “dimensional” or “immersive” audio becomes a new frontier for exploration in telephony. In fact, in some limited ways we’re already doing this in larger video conference room & telepresence suites.

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Pink Floyd: The Making Of Money & Directionality

pink-floyd-dark-side-of-the-moon-160On the surface this might seem a wee bit off topic, but bear with me as I will get there eventually. My thanks for Crunch Gear’s John Biggs for pointing out this You Tube clip documenting the making of the song “Money” by Pink Floyd. I’m a fan of the band and have also followed their individual solo careers in more recent years.

Further, I’m a big fan of Alan Parsons, who engineered a number of the bands recordings. Alan appears in the clip as well. He’s a master recording engineer which is something that I especially admire, having spent a portion of my youth in such endeavors myself.

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