It’s a high pitch and an occasional extra squeal which makes me think there is just a little too much room at a mating point between a diaphragm and a mating surface (like a balloon passing air when you stretch it).
I have baselined the carb by turning the idle mixture screw 1.5 times out and the idle speed screws - from the top of my head - 2.5 times in (according to Uncle Tony’s advice). I didn’t have the time to optimize idle screw with warm engine.
