"Erik Squires" wrote in message
rvers.com
Robert:

Right, I think the debate over 40 kHz signals and whether or not they
have any effect on us at all is cool, but not what I wanted to ask.

I'm more concerned with how good 3 samples is at 15 kHz, which I can
hear, albeit weaker every year.

So, 3 points in time, separated by 1/44,100 of a second, with 15 bits
of resolution (plus the polarity bit). Can this really define any
sine wave accurately?

It only takes slightly more than two points to define a steady sine wave.

What about a decaying sine wave, one who's
amplitude is decreasing linearly or logarithmically with time?

That takes a set of points that defines a slightly decaying wave. They would
extend over the duration of the decaying wave. If the wave is decaying
slowly, that would be lots of points.

Can a mere 3 points really stay true to this, even without getting into
discussions of linearity of a DAC at -90 db.

Most DACs are actually quite linear at -90 dB, given a properly-dithered
signal.

This is my real interest in high frequency recordings. I don't
intend to go out and buy a super tweeter.

Been there, done that.