As we’ve touched upon elsewhere, tunnels are somewhat stressful on a bike. Some are narrow, damp and poorly lit. Others are wider and have a sort of pavement either side. Despite this, we find that they create a sense of foreboding. Not least because of the sound.
This recording was made inside a tunnel, in a little layby, with the microphones perpendicular to tunnel. It’s of a small car passing. As you will hear, the tunnel makes for a much louder and confusing sound. One that is hard to place. Now imagine many (and larger / noisier) vehicles in the tunnel at once.