my mother just asked my dad's PD dr about possible speech therapy as his voice sometimes gets weak.

But the dr said it is just something that happens with some PD ers.

she did say dad seems to be holding his own fairly well so far with activities and mobility. he does have DDD -degenerative disk disease & pain from that.

but speech therapy is available , so you might want to look into for your dh, to see if it might be a benefit in his case.