My friend requested a knit tube 18”x4” to try putting over his headphones so maybe they wouldn’t catch on his hair, so I did a 2x1 ribbed tube and we’ll see how it goes. (It took me a bit to do it because I didn’t think it stretched enough the first time, so I redid it.)
I used my headphones for the second photo, but his are a bit bigger.

Update: It seems to work! He seems pretty pleased with it, and apparently even got some compliments from strangers on it. It adds a bit of cushy padding, which is comfortable but also warm. I’m considering making another with thinner yarn.