Online Hearing Test

Online Hearing Test was a Flash screamer prank by the website Liquid Generation, part of their long line of Sabotage pranks. The screamer was taken down along with the entire website.

Content
The game presents you with various sound effects to listen to in order to see if you can tell which channel you're hearing it from. With each sound, the player is given three choices: "Left", "Right", and "Can't Tell?". The sounds are played at a rather low volume, which of course would encourage the user to turn up their speakers. After a while, a white monster face appears with a series of high-pitched screams. Afterwards, the normal Liquid Generation Sabotage jingle and ninja appear.

Link
NOTE: The following video contains a screamer.

youtube.com/watch?v=-4cX7g2ToQM (can be seen at 2:20 in this collection)