Audio Hiccups After Sound Normalization

What you need to remember about the Normalisation functionality that Captivate offers is that it only gets applied to each individual clip separately, not across all clips in the project.  So, the normalisation algorithm will evaluate each clip you apply it to based on that specific clips dynamics (where the highs and lows are).  A clip with a volume spike somewhere in the mix will throw off the normalisation towards the higher volume.  That will then mean that particular clip will sound louder than the others around it.

That's why Lieve suggested using Adobe Audition.  It has the ability to take all of the clips from Captivate and normalise them as a batch to create a much more even treatment.  Even then you might find some clips will need to be tweaked.

Another related issue that can cause big variations in voiceover volume is to be standing (or sitting) too close to the microphone when you are recording your voiceover.  Professional artists usually recommend standing about 30 centimeters or 1 foot away from a large diaphragm microphone when recording.  (Yes I know that some singers like to almost 'eat' the microphone so that they get a bass boost to their voice when singing live, but that approach doesn't give you any room to edit.  Bass can be added later in the editing software if you need it.)  If you stand away from the microphone, the volume will be more even and normalisation will work better.  Try it next time.

Personally I never use the normalization feature in Captivate but take the audio clips to Audition. You can use fre  Audacity as alternative, if you do not have a CC subscription. Audio editing in Captivate is very limited, too limited for my musician taste. In Audition I can not only normalize with control of the normalization but have all clips converted to the same 'loudness' (which something else, don't want to be too technical).

Tips when recording: try to do all the recording for a course in one flow. If you need to split, use the same moment in the day because a voice can change a lot. Find the 'sweet spot' for your microphon or use a good quality headset where the distance to your mouth is fixed.