Follow-up: iMovie audio softer than original
I have been experiencing the same issue that a previous poster (Carolcarolcarol) described in their archived post:
iMovie audio softer than original - Apple Community
When I import video clips to "Project Media" in iMovie, the volume of the imported clips seems to be greatly reduced. I only discovered the problem after spending considerable time on an iMovie Project and exporting it. The exported/completed movie was way too quiet.
This apparent volume reduction occurs with video that has been imported from a file on my laptop as well as with video residing in iPhotos.
SOLUTION (for my case):
Looking at the Equalizer settings, it seems like the Default setting is "Flat." In my case, this was the problem.
Changing from the Default setting to "Voice Enhance" brought the volume up almost to the level of the original file and changing it to "Music Enhance" boosted it beyond the original volume.
If there were an Equalizer setting of "None" or "Original Sound" in which the volume/EQ were not affected, I would choose it. But, with the options given I'll probably go with "Voice Enhance" and definitely not the Default. Guessing this might be helpful to someone else...