Haunted Mansion and similar rides?

The Haunted Mansion is a slightly different animal than other dark rides.

Traditional dark rides are a series of scenes, sometimes with tricks such as a creature jumping out at you. These tricks were triggered by switches (once mechanical, now electric) and the audio for each scene was localized at the scene. Snow Whites Scary Adventures, for example, has audio at each scene, triggered effects like the beautiful Queen turning into the crone, and triggered audio as well. The thing to remember about these triggers is that they also need time to reset, so there's more distance between the cars.

The Mansion is a continous chain of cars, so the Imagineers had to do something different. Scenes had to be quickly viewed and nothing could reset. Also, the use of the clamshell Doombuggies on pivoting axis allowed the Imagineers to point your attention in a specific direction. And because the cars have internal speakers and always travel at the same speed, it was possible to create an audio script timed exactly to every scene (although I think Leota's Crystal Ball audio is played from her scene and not on the Doombuggies' audio soundtrack in order to sync with her mouth movements. I could be wrong though). And the narration is staggered from car to car: the car in front of you hears their narration a second before you do, a second before the car behind you, and so on. You'll also notice, if the cars ever stop, that the audio in your Doombuggy stops as well with an announcement about playful spooks. This delay allows you to pick up the story when your cars start up again.

The other thing the Imagineers did was to sync all the music in the Mansion. Many of the scenes back up to one another and Walt didn't want any audio bleed. So each scene is playing a variation of Grim Grinning Ghosts.

Recently, a decision was made to increase the speed of the Doombuggies. The result was that a few lines of the Ghost Host's narration had to be cut to keep the audio paced with the cars travelling at a faster rate.

Basically it is the car moving at a specific speed breaking an electronic eye, which then activates the scenes and sequences.

Them engineers at Disneyland are worth every penny. Alot of Imagineering.