[Arny Krueger[_4_]]

"Neil Gould" wrote in message
...
Arny Krueger wrote:
"Neil Gould" wrote in message
...

Please explain this, as it is not something I've experienced in over
25 years of editing digital audio. There is no amplitude in the
signal at zero-crossing points, so how can it possibly result in a
click?

Just because you're merging two clips at a zero crossing doesn't mean
that there isn't a difference in the DC levels of the two clips. It
is the difference in the DC levels of the two clips that causes the
click, pop, or thump.

Perhaps we're talking about different kinds of "zero", Arny. 8-)

There are two different concepts at work here - the instantaneous value of
the wave at its end points, and the average value of the audio clip.
Consider an audio clip that is zero at both ends, but entirely positive for
its duration. Its average value is clearly positive. If you splice that clip
between two other audio clips whose average value is zero, then there is a
DC pulse whose duration is that of the middle clip.

Audio signals are generally asymetrical, which means that only special cases
of them actually have an average value of zero. The easiest way to contrive
these special cases is to high pass the signal with a filter that has the
highest corner frequency possible.

When put high pass filters on microphones to control low frequency noise,
proximity effect, and popping, we accomplish the reasonable goal of having
signals that are easy to splice without adding clicks, pops, or thumps.