Software development, engineering, mathematics (in industry rather than academia).

The loss of signal could probably be eliminated in all of these, with some effort. The sort of thing I'm thinking of where signal would be lost by default is where you ask the interview candidate to design something, write a bit of code, sketch a system they worked on in the past, etc., on paper or whiteboard. If the candidate has to be behind a curtain, that's difficult to do and probably involves irksome extra latency (e.g., a system where they write or sketch whatever they want to and then step aside, and only then does the interviewer get to see what they did).

You could work around this with computerized whiteboards -- the candidate sits in one room and the interviewers in another, both rooms have electronic whiteboards, and they are coupled so that anything written on one shows up on the other too.

(Or by using something other than whiteboards that's easier to decouple in this way. For instance, for a coding task some kind of collaborative text editor may do better.)