The first time I realised how important it is to keep the microphone protectors clean, happened when a recipient reported the following observation: "I think I'm going mad! When I walk towards my television the sound becomes softer, and when I walk away the sound becomes louder!”. Well, a bit of detective work showed the microphone protector was the culprit. Both the Freedom and CP810 processors have two microphone entry ports - these are two tiny circles in a row (front and back). All the sound in the environment has to enter through these tiny spaces to be processed for listening. If the front microphone is blocked (with perspiration or dust which is easy as it is facing up towards your scalp and hair), and the back microphone is not blocked, the sound coming in from the front will be softer compared to the back - therefore explaining the "crazy" experience above.
Lesson: To avoid a trip to your audiologist to 'do something about the background noise’ make sure you change the microphone cover once a month (white insert) or every three months (grey insert) so that you hear more speech and less background noise. If you are likely to forget this regular procedure then mark it in your calendar or diary.