I knew that sounded familiar! "In The Dark Knight and the follow up The Dark Knight Rises a Shepard tone was used to create the sound of the 'Batpod' - a motor

I knew that sounded familiar! "In The Dark Knight and the follow up The Dark Knight Rises a Shepard tone was used to create the sound of the 'Batpod' - a motorcycle that the filmmakers didn't want to change gear and tone abruptly but to constantly ascend."