Portal 2


When using the orange gel in Portal 2, the player speeds up rapidly and is capable of moving at very high speeds. This speed is accompanied by a sound effect that seems to get higher in pitch and more intense the longer you are moving. The effect gives the player a more immersive sense of speed, and gives you a good sense of how fast you are going at any moment.

(In case the link doesn’t work properly, the sound effect is at 1:40:09 (h:m:s))