“Masking Threshold” a fascinating experiment in intimate, minimalist horror, showing just how far a filmmaker can go with an idea, a camera, a single setting and a simple premise — showing a man’s psychological collapse documented via an online video diary.

Filmmaker and star Johannes Grenzfurthner gives us mere sections of his face and parts of his body, only seen full-on from behind as his unnamed character “experiments” on his maddening tinnitus and takes us along for his “research” in a self-narrated descent into madness.

In a montage of extreme closeups of what our stricken, misanthropic and gay University of Central Florida alum and miserable Apopka, Florida recluse sees, reads, dissects, eats (jam toast) and trims (his toenails), we see how his world has closed in around him.

Grenzfurthner hired actor Ethan Haslam to ramble, criticize, fume and fuss over his efforts to “cure” the hearing condition that has utterly consumed him and is turning him into a misanthropic loner.

“Tinnitus,” he reminds us, is “the hearing of sound that has no external source.” Something happened to this one time physics student at school that put a noise in his head that will not go away.

And as “the miserable have no medicine but hope (slightly misquoting Shakespeare),” he decides to do his “own research” — questioning, reading, dabbling in chemicals and bizarre bursts of sadism in search of some means of curing himself.

“Masking Threshold” is a term from auditory research about relative sounds, the louder one being that which the ear can discern and concentrate on.

Our anti-hero rages at “ignoramuses,” his boss (“leadership skills of a squirrel”), his work, his mother and even at his new neighbor (Katherina Rose) as he spirals down that rabbit hole and the myriad detours his mind takes him into along the way.

He boils this or that in a bunsen burner, rants about religion, quotes composer John Cage on “silence,” and fumes at how little help the various hearing and acoustics forums are online.

“It seems the only way to get the right answer on the Internet is to post the WRONG answer.”

Long before we see him fiddling with slugs and worms, “experimenting” on parakeets and beheading mice, we’ve figured out he’s lost his Apopka-picking mind. He lets slip that he’s been in therapy, insists he’s attempting “unconventional and yet solid approaches” to his problem. There’s no way he’s making “progress,” but he’s adamant that he is and that it’s publishable.

“My research will NOT end up as epistemological road kill!”

What emerges is a thorough and thoroughly disturbing portrait of a man built from snippets of speech (he’s very articulate and smart), glimpses of body parts and filmed actions ranging from reading and grooming to putting jam on toast, fingering the scars his abusive combat veteran father gave him.

It’s a narrative experiment (not unlike Derek Jarman’s “Blue”) that makes the point that sometimes, you don’t have to see someone’s face to paint in every detail and figure everything you need to know about him or her.

“Masking Threshold” isn’t for everybody, or even every horror fan. I found it occasionally repellent, and mesmerizing in a droning-on to-the-point-you-tune-out way. But even at its most unpleasant, it’s never less than fascinating

Rating: bloody violence, implied animal abuse

Cast: Johannes Grenzfurthner, Katherina Rose and the voice of Ethan Haslam

Credits: Directed by Johannes Grenzfurthner, scripted by Samantha Lienhard and Johannes Grenzfurthner. A Drafthouse Films release.

Running time: 1:31