What causes the sound of climaxing bees?
Firstly, those aren't bumblebee faces ... those are big fly eyes. Those are Bumblebee Hover Flies (Volucella bombylans):

The noise in the first part of the video is identical to a fly flying around your head and the noise at the end sounds like what a fly would sound like when you press it against a surface like a wall or screen (or a newspaper, apparently)