I have ongoing problems with sound quality due to my Phonak Smart XI microphone screens getting gunked up. They are easy to replace but it requires a long trip to the audi to get replacements. The indications that there’s a problem are increasingly muffled sounds and “scritching” noise from my hair across the screens.
I have discovered a cleaning routine that seems to work well. First, I remove the dirty screens then soak them in alcohol for about half an hour. Then, I dry them on a paper towel and holding them firmly blow them out using canned air (the kind they sell to clean electronic components). Warning: hold on to one end of the tiny screen FIRMLY as the force from the canned air will launch them into orbit if you lose your grip. I grasp one end, blow out the other and then reverse my hold and blow out the other end. I also discovered that blowing them out from both directions helps. Using a magnifier you can see the before and after results.
I have two pair of these little screens and alternate them about every two weeks and have done so several times with good success.
I hope this helps someone and will welcome any further suggestions on how to deal with this problem.