If you enter a dialogue with someone who is playing a different radio station in their house/bar/ or whatever than your pip boy's radio, they both play at the same time. So you have two radios and the characters voice going on at once. You would think one would be faded out. Yes I know I could turn my pip boy off, But who remembers to do that each time? It's just way too much background noise while you're trying to hear the dialogue. I think if any changes or improvements were to be implemented in the next patch, this might be a good one to consider.

Its even more annoying during a game caravan.

Yeah I hate that too I haven't run into it much though. While I enjoy the DJ's comments I can't really say that I get into the music very much. It's not really my kind of thing (country/oldies) and when it starts repeating I have to kill it or myself. I much much much perfer the game's ambient music that plays when your pipboy's radio is off. Great atmosphere.

This is why I play with subtitles on.
Also it helps me blast through boring dialogue as I can read much faster than they can talk.

I just made my own post about sound on the PC version. Seems to me the sound for music, effects, and dialog were more distinct in FO3 then in FONV. FONV is the poorer for that. I can barely make out what's being broadcast on the radios. And yes, I did work the sliders in the options screen. And I'm still playing FO3 on the same rig, so its not that.