[elmoe]

More than likely you are picking up fan noise. Have you tried removing the laptop's cover and cleaning the fan?

 

[mannitheear]

I have found this topic because I have a similar problem: high pitch noise with USB audio on a Macbook Air. The noise is very quiet but nevertheless it should be not there. It's independent of the source software (Safari, Qobuz, Audirvana, Roon...)
Meanwhile I'm sure that it's not a hardware problem and no EMI phenomenon, because if I start the same hardware configuration with my Bootcamp Windows 10 partition it's absolutely quiet using foobar or AIMP.
My conclusion is, that problem is caused by the OSX/driver software stack, but I have no idea to solve the problem.

 

[bigshot]

Take it in to an Apple Store and have them look at it.