Why do the Captain in every flights have that static noisy voice?
I was listening to a podcast with Michael Dorn (Worf from Star Trek). He was talking about how it isn’t something that is actually TAUGHT to pilots, but just an interesting phenomenon that many of them talk like that. It’s a combination of trying to focus on multiple things while relaying information along with the set idea that that’s how pilots talk. A person’s personality changes when they get on the overhead microphone as a pilot.
Are you talking about PA announcements made by flight crew to passengers on commercial aircraft?
The flight deck is a noisy place, and the interphone (the handset they used to talk to cabin crew or make announcements) is not designed primarily for studio-quality sound. But it really depends; I often hear announcements that are surprisingly smooth and fine-sounding.
If you’re talking about air traffic control recordings that you might hear online, it’s because the communication link uses old-school VHF radio transmission with a narrow voice band and which is very susceptible to interference (much like old AM radio).