Most hearing aid manufacturers today claim that their aids are “water resistant”. But don’t be fooled. Are the aids better under conditions of moisture than a year ago - YES. Are they waterproof - NO.
Each company has their own little way of setting up casing and mics and receivers to make it as resistant to moisture as possible. Some use rubber to seal casing seams so moisture doesn’t work it’s way in. Some put gortex linings around mics so moisture doesn’t ruin them. I know for a fact and for experience that these processes do actually help to make moisture LESS of an issue. But no one will be able to get away without a couple of hearing aid repairs due to moisture in any hearing aids lifetime.
Plus, the zinc air batteries have to be exposed to air, hence the little slits or holes in the casing around the battery compartment, so that spot is always left at risk for corrosion from moisture. And with some aids, if corrosion happens, your audi won’t be able to connect the aid to the software for programming.
So yes, they are water resistant, just not waterproof (no matter how much rain the manufacturers dump on aids in their marketing materials