Third Audio Sample from Trek01

For this next sample, I remained at the same location, the Midwest Tunnel in downtown Milwaukee, but I exited the inside of the structure and stood outside the east exit. This tunnel is approximately 150-200 yards long, long enough for the entrance to appear rather small from my perspective. As the cars approach the exit, their noise becomes immediately louder just before they emerge from under the tunnel, so that told me that the expanse swallowed up and dispersed most of the ambient noise. But what I did notice is that louder, higher frequencies defeated the man-made buffer and did a fine job of exiting at the point I was standing. A prime example would be emergency vehicle sirens.
This third sample is exactly that, the remains of the emergency vehicle siren as it passed the entrance to the tunnel. Or at least I think it did. I actually never saw the vehicle go by, only heard it. It came upon me suddenly, like an air pocket opened allowing the stronger frequencies to reach me, and it left me just as quickly.
When you listen, notice that the back-traffic appears muddled, and the fore-traffic is clear, but over it all is the ethereal siren.

Tunnel Sirens