[sdiy] Formula for Audio & Log-taper pots?

[Glen]

I need to explain to a programmer friend of mine the difference between
linear, log, and audio tapered potentiometers. All the controls on his VSTi
are linear taper, and some of them should definitely be either be audio or
log taper instead. Explaining linear taper is so simple, I don't even have
to do it.  ;)

I've read that audio taper pots have 15% resistance at the half-way point
in their rotation, and that log taper pots have 10% resistance at the
half-way point. Is this generally correct?

Does anyone know of a more precise way to describe the "curve" of either
the resistance vs rotation, or more importantly, the attenuation vs
rotation? I would really like to find a formula to calculate the
attenuation for a given amount of rotation. I'd also be interested in a
chart of the same data. I need something that will be crystal-clear to this
programmer friend of mine. I'm not sure if just specifying the mid-point
resistance would be enough for him to properly emulate a given taper.

Unfortunately, I don't have any loose pots laying around to make
measurements of, at this time. So, I thought someone on the list might
happen to know the answer.

thanks,
Glen
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