So someone might have already found this, but in the second part of Test 15 (where you have to press the buttons at the same time and open the doors for the energy pellet) there's a place you can get trapped. This is not the creepy part and I'm sure someone has found this: you press the buttons at the same time, then quickly launch yourself from one of the button rooms and use momentum and portals to get into the same room as the energy pellet receiver.
Here's the creepy part: There is a radio in that room, and when GLaDOS opens the escape hatch, finish the test properly, and take it with you to the elevator. Then, at least for me, the red sprite turned green and it started making a bunch of strange beeping sounds. If you take it into the fizzler, a really strange sound effect plays that sounds like someone screaming or dying.
Anyone else found this? I almost shut off the game when it played the sound XD

Hmmm it sounds for me a little bit like Atlas, or a Angry Core ^^

This was part of the ARG that Valve released a long time ago IRRC. The radios play the dinosaur_fizzle sounds or something.

Darn, I was hoping it was new.

That's the old P1 ARG. Run the radio sounds through an SSTV decoder.

Can anyone tell me how to get there =-=
I'm trying to get that achievement
I need to know where the other radio signals are and how to get to them. (Especially 15!)
Also how to get the other radios. I've found 18/26 on my own but now I'm stumped D:

Also the creepy sound that plays when you fizzle a radio.
"I heard that" ...... that's what it sounds like.
I do like how the turrets go "onnonononoononono" when you fizzle them XD

There are plenty of walkthroughs on Youtube if you need help.

I think it was part of the achievment Transmission Received where if you found a radio and brought it to a specific location your raidio would receive a different signal, the light would turn red and play some random static noise. And if you find all of the radios you get the achievement Transmission Received.

Here's a walkthrough to find all the radios and get the achievment http://strategywiki.org/wiki/Portal/Tra ... n_Received