When thinking of Parkinson's disease, we usually think of tremors, but there is another problem that may be even more frustrating to the patient; trouble talking. This is such a common obstacle for Parkinson's patients that the problem has its own name. It is called Disarthrea. It's not that they can't talk but that their speech becomes softer and harder to understand. The good news is that, with rehab, their voices can become better.
Speech Language Pathologist Kymberli Dixon says, "It's difficult for them to gauge the amount of loudness or effort that's required for them to be understood at a normal conversational level. You're talking about one month of treating a patient and seeing a life change in four weeks". Dixon is talking about a treatment option in which therapists use a ‘sound pressure level meter' to demonstrate how loud a patient speaks and to bring the voice to a level where it can be more easily understood.
If you know someone whose voice has become increasingly softer and harder to understand (whether they have Parkinson's or not) they might benefit from a speech pathologist who could let them know what kind of volume they have now and how to bring it up.