hm...
from an electricity standpoint (bear with me here.....) AC alternating or changing current makes noise....DC doesn't. A waveform is alternating, and so we hear sound. When i was a tyke, i hooked a 9 volt battery up to a tiny speaker, and heard no noise...except for A tiny click...temporarily (the quick click...) the voltage was changing...from 0vdc to 9vdc.
hats this have to do with me and MY situation? glad you asked...when i was cutting and pasting between 2 waveforms, I got "clicks" at most of the attachment points ( I use Cool edit pro, too...lol) I was like what the HELL is that clicking? So's I r-e-a-l-l-y zoomed in (alt-rightarrow like 12 times...lmao) on teh waveform like i had a digital microscope, and at the molecular level (lmao, kidding...) i found the clicks.....i had cut and pasted over the existing waveform, yet taken no care that the waveform was "even" and "smooth"...this sudden instantaneous jump in voltage was JUST like the click when attaching the 9 volt to the speaker.
TIP: have area before and after the part youre splicing in you can really zoom in on to "line up" the waveform where the new waveform touches the "old" one...this eliminates the click.
now, this is the "longhand way"...if i had to guess, there a setting somewhere for "zero crossing editing" or some such shit, and i strongly suspect they will do what i just described for you, automatically, consult the manual on zero crossing, but if not, the longhand method will eliminate the click. Just rememebr the click with a 9 volt toa speaker, and you wont forget it. Remember, the "waveform view" is really a virtual oscillioscope, and sound is voltage versus time. you always want the waveform to be s-m-o-o-t-h,
