Yes, I know this well. I developed a hoarse voice within days of coming down with ME. Others didn't seem to notice, but I could feel (and hear) the raspiness in my throat. If I spoke more than a few sentences, I would get a sore throat.
I’m not sure if it’s related, but today my voice instantly becomes “gravelly” if I try to talk at a volume between that of a normal speaking voice and that of a low yell that would carry across a room. Unlike the hoarseness of my normal voice, this change in vocal quality is quite apparent to others. It invariably occurs when I try to talk to someone in an environment with modest background noise, such as in a restaurant.
Strange thing is that this only happens at some mid-range of volume above a normal speaking voice and below a flat out (but not screaming) yell.
I’m not certain that it’s related to ME, but it didn’t happen before I got ill. I suppose it could be acid-reflux as suggested, but I suspect it’s more like a “hand tremor” in the throat that results in a certain loss of fine control of the vocal chords (or something like that...)