This corridor also widens at the end, but downwards as well as up and to the sides. Shining the torch around, you can see that your passage has opened up to branch onto some kind of tube, about three metres in diameter. The walls are made of what looks like dark glass or obsidian, perfectly curved, and remarkably clean. There is no trace of mould, lichen, moss or waste leaf matter anywhere around the reflective inside surface of the tube.
Looking around with the light, you find that a little up and to the left on the other side of the tube is an exit, smaller than your own, but still large enough to fit into. The tube itself extends further than you can see to the left and right.
To the left there is a faint light source, barely enough to cause anything but glinting. The rushing, flocking sound is coming from that direction too, but very quietly.
You have several options.
Zing - wait and see if anything happens
Zing - use an item you are carrying
Zing - hop down into the tube