[JohnM]

Some ripple in the loopback measurement at very low frequency can occur if the soundcard has very extended low frequency response, those ripples can be removed by increasing the impulse response window width (the ripples are an artefact of the window truncating the response before it has fully decayed into the noise floor). Ripples in the midrange of the soundcard cal would suggest feedback from monitoring being active, that needs to be fixed to get a valid cal result.

 

[JohnM]

For the Audigy 2ZS the advanced controls, accessed by clicking the red + in the REC section of the Creative Surround Mixer, have a check box for "Record without monitoring" that needs to be selected (under XP at least, may not be applicable under Vista).