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The PNW Section's January 2007 meeting was an all-day Saturday workshop on digital filtering. About 30 persons (21 members) attended. The meeting was held in the Northshore Performing Arts Center auditorium in Bothell, WA. Chair Dan Mortensen opened the meeting and had everyone briefly introduce themselves.
The presenters were:
- James D. Johnston - received the BSEE and MSEE degrees from Carnegie-Mellon University, Pittsburgh, PA in 1975 and 1976 respectively. JJ temporarily retired in 2002 after working 26 years for AT&T Bell Labs and its successor AT&T Labs-Research. He was one of the first investigators in the field of perceptual audio coding, one of the inventors and standardizers of MPEG 1/2 audio Layer 3 and MPEG-2 AAC, as well as the AT&T Bell Labs or AT&T Labs-Research PXFM (perceptual transform coding) and PAC (perceptual audio coding) and the ASPEC algorithm that provided the best audio quality in the MPEG-1 audio tests. Most recently he has been working in the area of auditory perception of soundfields, ways to capture soundfield cues and represent them, and ways to expand the limited sense of realism available in standard audio playback for both captured and synthetic performances. He is currently employed by Microsoft. JJ is an IEEE Fellow, and AES Fellow, a NJ Inventor of the Year, an AT&T Technical Medalist and Standards Awardee, and a co-recipient of the IEEE Donald Fink Paper Award.
- Steve R. Hastings - an experienced software developer and a free software enthusiast. He has been keeping track of the free software community for about a decade. In his current job he is developing a general-purpose audio DSP engine, using the C programming language. He enjoys listening to jazz and progressive rock.
- Bob Gudgel, K7IQ, has worked with, or for many Northwest audio companies, including Phase Linear, TAPCO, Spectro Acoustics, AudioControl, Mackie, and Symetrix. Bob presently works for Magnum Energy Inc. designing inverters/chargers for the alternative energy market, as well as spending time at side jobs related to audio and his home recording studio. Bob also runs a web forum for defunct Northwest audio companies that can be found
here.
In the morning session, "JJ" Johnston started with a simple analog filter as an example and expanded on the discussions that started with the Section's prior workshops on FFT's and on digital-to-analog conversion. He reviewed the basics of digital filter design, and discussed the practical aspects of the theory and issues that relate specifically to digital filtering.
After a no-host lunch, door prizes were awarded:
- Audio CDs from Starbucks/Hear Music:
- Rick Rodriguez
- Matt Castle
- Jeff Hammerstrom
- Rick Chinn
- a copy of Tinnitis Today magazine, Steve Macatee
- a copy of Funny Times, Dan Tebbs
- an AES Exhibitors directory from the 121st convention, Ray Miller
- Wavetek meters courtesy of Rick Rodriguez and Fluke:
- a color photo enlargement from JJ Johnston, Daniel Casado
- a gallon of bleach, courtesy of a neighbor of chair Dan Mortensen, Steve Wilkins
In the afternoon session, Steve Hastings and boB Gudgel described how to find and install freeware computer software that help design and implement filters, and showed what happens to actual audio signals when you do, in fact, filter them. Steve described some different forms of "free" software, such as "shareware"; then software that's free but with terms; open source; and free with no strings (his preference). He also showed a popular free, multi-platform audio editor, Audacity. Bob began to exhibit filters on a typical DSP card, but unfortunately ran into a host of technical difficulties and shortened his demos.
Reported by Gary Louie, PNW Section Secretary
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