Weird. American air carriers have required liquid-resistant designs
to "pass through" liquids to the floor through drain holes in the metal boxes for decades.. At least for the intercom panels that I worked on.
One US airline went through a "waterproofing" retrofit company-wide more than a decade ago. gaskets around the knobs. Plus, aircraft circuit boards are required to be "conformal coated" to also mitigate humidity and corrosion. Do a repair? Put more coating back on.
Audio control/intercom systems on single-aisle aircraft are sourced/customized by the airlines and installed by Boeing and others, like Bombardier. It's a lucrative racket if you can meet the documentation and testing requirements without losing your mind.