Greetings community. I made a thread a while ago talking about this audio issue I was having, and may have found a fix for it (however, I don't know if anyone is having this same exact problem I was having)

Basically, I would walk to certain areas around the wasteland, or walk into ANY casino for example, and my audio would completely go silent until i went to another area in the game where the audio would go back to normal.

Found this out on accident, but here's the steps I followed.

1) Alt+Tab to desktop
2) Click your sound settings on the taskbar [the speaker, that looks like <))) ]
3) (I have windows 7, so it may appear different on yours) - Click Mixer
4) http://i56.tinypic.com/263ykwx.jpg This is what was happening in my volume mixer; New Vegas would force itself down to a lower volume and stay there for a while.
5) Simple drag the slider back up to full volume, (keep open just in case it goes back down) and alt tab back in game.

Your sound shouldn't drop anymore, no matter where you wander to.

This is a fix that works for me so far, let me know if anybody else has any success with this.

Side note - I honestly do not know what is causing my volume to drop down, but something was causing it, and increasing the volume back up solved the problem (granted, i have to do this everytime I launch the game, but that's no big deal)

Very interesting the game turned down your sound. No idea why... perhaps something was recorded at a higher volume than other things and it was simpler to program the volume to drop... dunno.

Thanks for posting what worked for you though