Sound effects supervisor Ben Burtt recorded the film's many sounds. The snake slithering is a mix of Burtt running his hands through cheese casserole and wet sponges being dragged across grip tape; the rolling boulder is a Honda Civic driving down a gravel hill; and the Ark lid opening is the sound of a toilet cistern being opened. The Ark spirits are the cries of sea lions and dolphins filtered through a vocoder. Jones' revolver is the sound of a Winchester rifle firing, while his whip-crack was made by recording Ford using the whip.