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Date:	Sat, 22 Dec 2001 20:43:21 PST7
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-help@scoug.com
To:	scoug-help@scoug.com
Subject:	SCOUG-Help: oscilloscope multimedia alignment

Content Type: text/plain

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Ray Davison wrote:
>
> Would wav files consisting of signals that
> run for some period of time be useful?
> Say a 1KHz square to check damping
> factor and step or sweep sine waves.
> Maybe a 20-20K log sweep with a 10 sec
> sweep time.

Yes, you've definitely got the idea. Sine, square and ramp (or
triangle) waves are pretty much all you need for audio testing. I've
never had a need for pulse testing, and the intermodulation distortion
test using two sine waves at different frequencies would be a fiasco if
you digitized it (due to the artifacts).

I was hoping there might be a utility that would simply generate the
waves or .wav files. I have the .WAV file format and I can write the
program, just didn't want to. :)

Sine waves (including sweep) are great for frequency response testing
and clipping. Square waves are used for ringing tests, though consumer
audio gear (= sound cards) aren't likely to have ringing problems.
Low-frequency square waves can also show power supply problems. Ramp or
triangle waves can quickly show hysteresis distortion and clipping.

There are some "exotic" waves which are quite useful, such as white and
pink noise, but I don't need them for what I'm doing. Pink noise is
handy for acoustically tuning a room; you can try to do it with a
slow-sweep sine wave but the nodes and nulls are huge even in the best
rooms so it's hard to interpret the results using a sine wave.

For minimum noise in an entire system, you set the gain of every stage
so the clipping points occur simultaneously. That gives you maximum
dynamic range, thus minimum noise, and is one great use for the
oscilloscope.

- Peter

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