Loudness of .Wav compared to .AC3

Ok, interesting problem I'm encountering in DVDA 4.0. I don't know if this is a flaw in the software, or if compression is being done to audio, when rendering it to the AC3 format. I'm using the EXACT same wave in Vegas, as the background wave for Menu 1 in DVDA. In Vegas, I rendered the audio out to AC3 to Prepare for DVDA. In DVDA, the audio track, for the Menu 1, is still in .wav format. The problem is this, though they are both the exact same audio track, the one accompanying the video (AC3) is substantially lower in volume, then the Menu 1 audio track. This becomes a problem, when the video ends, and the menu background audio plays............though it's the same file, it's much louder! Making the product seem amateurish. This is a music video btw, and the audio is a crucial part of the production. I prefer the loud track of the .wav as opposed to the subdued AC3, if that makes any difference. Any direction is greatly appreciated!! I guess you will probably say that once the DVD is Prepared the .wav too will be rendered to AC3. True, but is there a way to preserve the loudness of the .wav file as opposed to the .AC3 file?