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A New Approach to Distortion Measurement, by Bob Smith


Dan Mortensen:
Hi All,

Our friend Bob Smith has had a life of measurements in his role as audio designer for Stryker/Med-Tronic/something else, where he super-refined the audio playback and recording aspects of emergency heart defibrillators. Those things have audio cues for what to do in a serious medical emergency which can take place in very noisy environments and need to be heard and understood without relying on simple volume. They also record what's going on for later evaluation for treatment/autopsy purposes.

Medical stuff is all super-regulated and overseen; his work was subjected to deep scrutiny and evaluation, and he basically re-invented that part of the industry. With a watt or so of audio power, and a 3/4" or 1" speaker, and not much processing power, he used psychoacoustics to make the devices understandable in helicopters and on casino floors and wherever else they were needed, with audio that's no louder than needed so it's not a distraction.

In his retirement, he's been looking deeply into audio measurements, among other things, and has come up with a semi-automated means of making distortion measurements for audio gear that, instead of yielding one number for distortion at one frequency and one amplitude, gives a field of numbers that look like a sheet of paper in a three dimensional graph.

Here is a video we made of the first time he showed this thing to an interested audience. As noted in the description, there is much work to be done on it, and this was done sort of as a progress report of a long project.

This was made last November, and it took me this long to realize this forum was part of PSW and that you might be interested in seeing what seemed revolutionary to me.

He's had some things since that have kept him from working much on this, but there's enough here to give you the idea that we could be on the cusp of having much more accurate and descriptive characterizations of distortion in real world conditions.


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