Monday, September 8, 2008

Changing the nature of sound

Through an odd set of coincidences, in the last 12 hours I read about two US tech companies that appear to have used digital communications technology to differentiate themselves. The common thread is their use of digital signal processing in portable handheld device to make sound better — possibly better than the original. Although neither of these is a San Diego firm, they both fit the broad brushes of the digitalization of communications that I’ve been studying in our planned book.

Since I bought my first audio cassette deck as a college student, the goal was to find a recording device that minimized the damage done in the recording process, i.e. the new noise that was allowed to intrude into the analog signal. I owned three cassette decks connected to my stereo from 1975 until I had enough CDs to give up on cassettes during the early 1990s.

While DAT and minidiscs were around since the 1980s, I bought my first digital recorder to record interviews replacing a series of portable cassette recorders the size of a paperback book. The Olympus DM-1 was among the earliest of the Olympus digital recorders, whose main attraction (at least for me) the ability to electronically back up research interviews.

But this morning I saw a link to the Zoom H2, a well-reviewed digital recorder from 26-year-old Samson Technologies. The H2 is a low-cost, miniature version of its earlier Zoom H4 portable digital recording studio.

What I thought was clever about the H2 was not the four-track recording for garage bands, but the use of the DSP and the four mics to electronically create different microphone response patterns — two different simulated stereo cardioid patterns, plus a symmetric omnidirectional patterns. Once upon a time we would buy different mics for different goals, but now (as with synthesized guitar amps) this can all be done electronically.

For my use in interviews (as opposed to recording my “band”), what surprised me was that they didn’t simulate a highly directional mic pattern, but maybe that’s a firmware upgrade. Still, with a street price of $170 it’s far more recorder at less money than what I bought five years ago from Olympus.

The earlier notice was one of those obscure, self-promoting trade magazine articles, in this case in IEEE Computer. The article by Lloyd Watts, founder/CTO of Audience Inc., talked about the challenges of reducing three different types of background noise you hear from cellphone callers. As with the H2, the solution combines multiple mics, a DSP and clever algorithms.

While Audience is interested in selling a specific chip (the Audience Voice Processor), the broader implication is that the ITU’s P.835 standard for noise reduction now accurately tests for the challenges of stationary, quasistationary and nonstationary noise sources. Cellphones reflecting this improved sound fidelity are shipping in Japan and Korea, and presumably will spread more broadly over the next few years.

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