Ted Griffioen has a new tutorial at Audio Tuts+ explaining the process of creating a Half-Life Monster Sound. Here is the introduction:
“If you ever played a game like Half-Life without sound you will acknowledge this: the scare factor comes, at least in large part, from the sound effects. Monsters don’t really seem dangerous if they don’t make a scary sound.
Close the curtains and inform the neighbors, because in this tutorial we will transform your own voice into a monster you never thought you had inside you!”