If you listen to it in the start of the sound, it is playing the radio music.
And if listened to it backwards, you hear somebody say "Is anybody out there? Can anybody hear this?"
1. Heard it, kinda makes the radio a nice sounding song to cover up a darker story...
2. I listened to it closely (not reversed) and it sounds like someone screaming "GET ME OUT OF HERE NO DON'T KILL ME" and at the end of the e in me the turret sounds start playing; I speculated it's possible that it's Ratmann being killed by turrets.
Edit: I'm snooping around my portal sound folder and turns out, all of the dinosaur_fizzle sounds sound like they have someone screaming, however the orginal one is the only one with words and the rest have more of "ahh"'s and "ugh"'s.