Last night I got to hear Jane Monshein at the Phoenix Musical Instrument Museum. Jane at 41 has a powerful, often quite high pitched voice! I did find that some songs I understood her words quite well, some I didn't. Whether this is due to how she sings at times, vs whether the mixing at the concert was fine for the jazz instruments but not as helpful for vocals, I don't know. More probably that as Cannga notes above, the music mode for hearing aids may disable a lot of the processing particularly for speech so that the music comes through. Yet not even two weeks ago Rodney Crowell's vocals were clear as daylight - but Rodney has a lower pitched voice, whereas Jane has a very high pitched voice much of the time! I will discuss this when I see my Audiologist this Wednesday! Once again the music itself was clearly better, more well rounded/3D, I could hear drum rolls and cymbals much better, etc like I've discussed before.
You will notice that speech nuance with women ,including the ability to distinguish one from another ,is lost much earlier than men's voices.