When I worked there casually in the early 1990s, it was a pretty exciting place to be. Still in its original presentation, after opening in 1987, it was tardis-like in its internal proportions compared to the exterior. At the time it was still owned by the group who also owned Friargate Wax Museum in York - a little gem, now sadly closed.
It seems odd now, but all the audio (music and SFX) were played from cassette tapes in double cassette decks in the control room where the air compressor was. Because you couldn't really appreciate a stereo field, each tape was actually two totally separate tracks on the left and right channel, effectively halving the number of tape decks required. I think there were about 8 audio tracks in total - some were shared in more than once scene. They all played continuously. The tolling church bell in the graveyard scene was always playing, and could be heard in the shop/admissions till at the entrance. Every 60 minutes the bell and eerie wind would stop while the tape switched sides, and we all used to stop momentarily because something was different in what we were hearing.
A lot of work went into the presentation and theming of the attraction, although I'm not sure who did it (I don't think it was an in-house job). There were, in total, around 23 wax works which were all of an impeccable standard (and very, very expensive). Some were animated. I think it cost £1.75 to get in back then. The smoke machines were from Martin (a Junior 700, Magnum 1600 and another that was stolen before I was there. The 1600 was stolen in the mid-90s). Triggers were via single infra red beams at about waist or knee height with relays.
I went through a good few years ago and felt sad at how it now uses basic physical techniques to scare visitors (hanging cloth, squishy floors, total darkness, loud screams). In my era it was very much the 'experience' - the odd fright mainly from a dark scene coming into action with lights, movement and sound breaking the quiet and surprising the guests, but it was something people of all ages enjoyed. Now I only think it's suitable for children and younger adults - certainly not older people.
If anyone else has any memories of the Dracula Experience, feel free to post a comment (you can do it anonymously).