Finally getting back to this after a few days away. Thanks for all the tips and debugging help, folks.
cdanteek: My version of VLC gets updated fairly regularly, so I'm running 3.0.6, the latest. My set top DVD player is a Toshiba SD4200KU; my set top Blu-Ray player is a Samsung BD-JM57 -- same lack of sound on both players as with VLC. And I'm using MyDVD to create a standard DVD, not a Blu-Ray.
Brendon: Thanks for the pointer to the DVD Audio Extractor. I extracted the audio from both the DVD and the VOB file. (Yes, I know, effectively the same thing, but the program allowed me to do both and I wanted to try it both ways for completeness.) Both extracted MP3 files are silent. VLC gives the following information for the extracted files:
It's hard to see how I've bobbled the Roxio installation a second time. I believe the next step is to do an installation from scratch on a different computer. It will likely be next week before I can arrange both the machine and the time. Since the computer I'll probably try that on is a slightly earlier version of this one but with a different set of audio drivers, it will at least give us another data point on audio hardware and drivers. Or, at worst, tell me that I'm messing up the installation in the same way each time.
Meanwhile, I'm open to other suggestions.