How to resolve crackling after moisture exposure in QC25's

Hello!

Currently, I’m getting very occasional— but nonetheless annoying—crackling in the earpieces of my Bose QuietComfort 25 noise-cancelling headphones. This followed a period of exposure to damp air in my canvas bag when I was unavoidably caught in wet weather. (Note: the headphones didn’t get wet.)

The crackling can be heard only with noise cancelling switched on. However, it isn’t caused by the noise cancellation and is is sporadic, occurring in the cans independently of each other. Nor does it matter whether the headphones are playing music, are plugged in, etc. The sound is how you might imagine that of a very sensitive microphone being brushed lightly with a piece of cotton wool. It usually lasts for a few minutes at a time.

The headphones have been like this for about six weeks. My guess is that moisture has gotten into the microphone compartments for the noise-cancelling system and that what I’m hearing is the amplified sound of water evaporating, but I could be wrong. I’d have hoped any moisture would’ve evaporated by now and the problem resolved itself.

So far, I’ve disassembled the cans (as far as I can without having to loosen any glue) and left them above a radiator, whilst also hoping to speed things along with light wafts of a hair-drier and a vacuum cleaner nozzle hovered over the outer microphones.

Does anyone know how this problem can be fixed? As a last resort, I could buy a spares / repairs set and replace the microphones.

Thanks for reading.