As discussed in the Technology section, microphones contain very sensitive components. Because of this, microphones are covered by some sort of mesh grating. The grating protects the microphone's diaphragm against dust and incidental contact. Hearing aid gratings do not provide much physical protection from drops and rough handling, so treat the two microphone ports with care. Hearing aid gratings come in different styles, but are typically either two separate pads (one for each directional microphone), or one long piece that covers both microphone ports.
Over time, the gratings can become clogged with oils from the skin, dust and other debris. It is good practice to incorporate a quick brushing into the daily maintenance routine of the hearing aid (e.g., before the aids are inserted in the morning). The manufacturer will provide a small, soft-bristle brush for this purpose. Watch the animation (Figure 1) for a demonstration of proper brushing technique. 1).
Less frequently, perhaps once a month, the microphone gratings should be replaced. Figure 2 shows how a small pick is used gently to pry up a microphone pad, which is immediately replaced with a clean pad by simply pressing it carefully into place.