What we've got here is a failure to communicate

I've never been a huge talker, or a medium one for that matter.  As self proclaimed King of the Introverts, I like to sit back and listen while adding just enough to keep a conversation going.  But, there's a big difference between not wanting to communicate and not being able to.  So much of our day-to-day lives depends on our ability to speak clearly and be understood. Some daily encounters may include:
Having to call the Doctor's office and schedule an appointment. Calling the pharmacy.  Run a meeting. Calling customer service because the store lost your shipment, talking to your bank or the insurance company.  The sales clerk at the store needs your phone number, or placing your order with the person behind the meat counter. These are just examples of when you know you are going to have to speak and can prepare for that moment. Unexpectedly running into someone you know, or getting a phone call that you must take are now frightening scenarios to me.    
In every instance of conversation you need to be understood. Unfortunately, Parkinson's may have other plans. For me at least, its become a huge problem, so much so, that I avoid contact where I can.  I may come across as aloof, or maybe just rude but its easier to avoid conversations when you know you wont be understood. 
So what to do?
For starters, I contacted my neurologist to make sure my DBS unit isn't the cause.  I had a thorough exam where my speech (and swallowing) were tested and retested with the unit on and off as well as my status in the medication cycle of either "on" or "off".  In my case, the DBS unit was not causing any speech or swallowing issues.
I then went back to speech therapy.  This time I tried the Speak Out Program developed by the Parkinson's Voice Project which is now available in many areas around the country.  They taught me some skills to  combat the slur that has overtaken my normal voice. They concentrate on getting your voice louder which is typical for most patients with Parkinson's.   However, my problem is more complicated and a quiet voice isn't where I am struggling right now.  It is the formation, stuttering and speed that I can't always control.  Their recommendations include slowing your speech down by thinking about each word and forming it correctly.  It does work, however I have trouble doing that AND having a conversation at the same time.  Throw on top of that another Parkinson's symptom like word finding and you'll see what I'm up against. Word finding, the occasion where you cannot think of the word even though you know the word and can describe it, is very frustrating. Take the word drain for example.  I've used that word many times and can describe its function however at that moment in the conversation where I needed to say the word.... Nothing.  I couldn't  come up with it. 
Forcing yourself to slow down and form each word makes it very difficult, for me, to have a quick conversation. The best way I can describe it is by relating to something I said years ago regarding swinging my arms when I walk.  I can do it when I think about it, but, as soon as I stop thinking about it, I stop swinging my arms.  For people that don't have Parkinson's the exact opposite is true.  Try walking and not swinging your arms and you'll see what I mean. When I think about what I want to say I forget to slow down and enunciate.
So, what do people do to try and help?  They hear your struggles and almost always try and finish your sentence for you.  Unfortunately, their idea of what I am trying to say usually isn't what I was thinking.  I've been misunderstood, and even said somethings other than what I meant just because it was they only sentence I could utter clearly at the time. I say things that I think are understood only to find out later that it either wasn't heard at all or the person got tired of asking me to repeat something and just nodded their head.  Oh, and for another level of frustration, try talking to one of those digital assistants like Alexa, Siri or Google.

I think that it would be safer if I handed out a card prior to any conversation:

Warning! - Person with Parkinson's

For those that have to interact with me, please be patient and assume nothing because you may or may not have heard me correctly.

There are 50 muscles involved in swallowing but over 100 could be used in proper speech.  With Parkinson's fighting muscle movements it seems impossible to hope that I will ever be clearly understood again.   Maybe its time to rewatch Cool Hand Luke.