I was honestly questioning whether there was something wrong with the wiring in my house that was causing this (after having multiple MacBooks with the same issue), because the alternative that a company of Apple’s size had such a basic issue seemed so unlikely.
Given that many (most, I'd bet, by far) people don't experience this while you've experienced it on several devices, I wouldn't give up on checking out the wiring in your house.
Unless you're running some serious industrial level machinery, home devices have nothing to do with power line noise. It's cause by the air around the lines and the condition of the lines themselves.
