Ears Open Eyes - sound technology - Technology Information - Column

Computer Technology Review, April, 2000 by Hal Glatzer

My ears have opened my eyes. In the course of producing an audio entertainment project, I realized that there are many more storage devices, formats, and media "out there" than I have been covering. I've tended to focus on large-file applications such as imaging and this is the first time in ten years that I didn't get to cover the great AIIM Show.

Yet now I know that audio apps also generate large files, which demand high-capacity storage, and that many of the available options in the world of audio production are formats I'd been overlooking or had simply forgotten about.

Imagine my chagrin, for example, to discover that the top-of-the-line recording medium in music studios today is [ldots] 2-inch reel-to-reel analog tape. That was the original videotape format, 40 years ago. Hadn't it gone the way of tail fins? Apparently, a key reason it's remained the medium of choice is because a 2,500-foot reel can hold 24 separate tracks for 30 full minutes.

Most recording is done on digital media and, to a computer after all, data is data no matter what it represents. At the level of sonic fidelity associated with professional audio production, sound waves are sampled at a rate of 48KHz (48,000 times every second) and are rendered digitally as 16-bit bytes of data. Each minute's worth of those sound-bytes (sorry--couldn't resist) in a single monophonic audio channel consumes 5MB of storage space. Stereo sound needs two channels, hence the generic rule-of-thumb is that audio requires 10MB/min.

Which is why a 650MB CD-R holds just over an hour's worth of music. Every studio nowadays has a CD-R or CD-RW drive, although many of them use the "stereo-component" versions that I think are unnecessarily more expensive and which use more expensive media (you're pre-paying royalties in case you should happen to duplicate copyrighted material onto your discs). Yet for day-to-day backups, the studio I was in uses IGB Jaz disks. Being magnetic, Jaz offers considerably faster throughput than the purely optical CD recording process.

Permit me a momentary digression here in praise of audio-editing software. On my project, they used a Macintosh app called Pro-Tools, but there are comparable Windows programs too. They display those digitally sampled audio files (e.g., spoken-word recordings) as analog sine waves, much like the traces on an oscilloscope. Each separate "voice" is shown as a separate line on the monitor. Then, with mouse and keyboard, individual segments of any of those lines can be highlighted, cut, pasted, or whatever, into any other line. It's like a word-processor, assembling a document from individual letters, words, sentences, and paragraphs.

Arthur C. Clarke once declared that, to ordinary people, sufficiently advanced technology would be indistinguishable from magic. Well, my engineer was able to take an "s" from one word and put it on the end of another word to make it plural. She could manipulate any or all of the data in my audio files in remarkable ways. Somebody who talked too fast could be slowed down without lowering his tone of voice and, in the musical segments, the pitch of an instrument's note could be raised (say from Bb to C#) without speeding up the tempo at which the tune was played.

There are a few points on which computer-ese and audio-speak nomenclature differ. When I'm getting multiple copies of media, I call it "replication," probably from having covered so many REPLITech shows. Folks in the audio business, though, say "duplication" and, while I was familiar with DAT--Digital Audio Tape--I seemed to be the only one around who called it by its computer-industry moniker: "4mm" or "DDS." The audio pros didn't even say "d-a-t," by the way; they say "dat."

For my spoken-work material, they recorded directly onto DAT media, but then, the studio engineers transferred my audio files to a hard disk drive in a desktop computer for editing, so they could have random access to every discrete sound. They did that even though the final product--no matter whether it's music or spoken-words--will ultimately be published in a linear format--in the case of my project: audiocassettes.

Speaking of DAT, have you heard of ADAT? I knew "somebody" was using analog VHS videocassettes for digital audio recording, but now I know whom. ADAT stands for "Alesis DAT," Alesis (www.alesis.com) being a provider of mid- to high-end recording and special-effects equipment.

ADAT is apparently very cost-effective in the music business. List prices of the drives start around $2,600 and they can record up to eight separate tracks, thereby enabling effects such as over-dubbing, which are not available in 4mm DAT (DAT also is limited to just two tracks). For media, ADAT drives take off-the-shelf, inexpensive S-VHS tapes: a two-hour ST-120 cartridge holds 40 minutes of 8-track digital, audio.

There was a couple of other storage options around the studios that I hadn't encountered in a long time. One engineer was migrating from Jaz disks to Castlewood's 2.2GB ORB disks. Both are magnetic and Iomega offers a 2GB version of Jaz that's backward compatible, but the ORB system is a lot cheaper.