Legend of Hell House, 1973.
Although it's funny that modern "reviewers" complain about the film's "horribly synthesized soundtrack," if it's just acoustic … though there are some looped-up tracks for the high-voltage scenes that I think they complain about.
It's really the first time a movie uses science against the paranormal – even though it's BS, it's an entertaining setting. The book on which it is based is a hair-doer (duh), but since Richard Matheson has written both, the overall theme is retained.
Yes, as in "I am Legend" Richard Matheson.