LEIGH SALES, PRESENTER: This story is about one of the strangest crazes on the internet.

Tens of millions of people are tuning into YouTube to watch complete strangers whispering as they quietly fold towels or brush their hair.

The feeling it supposedly creates is known as ASMR, which stands for Autonomous Sensory Meridian Response. Enthusiasts describe it as a kind of bliss.

It sounds bizarre, but it's hugely popular, including in Australia, as Conor Duffy reports.

MARIA, GENTLE WHISPERING, ASMR ARTIST (YouTube video): Good evening. This is Marie again with you. ... (Inaudible) have my wonder brush. I turn into the sound of it when you run your fingers over it.

CONOR DUFFY, REPORTER: It seems like the most boring video in the world. But more than seven million people have viewed this 16-minute clip of Maria, Gentle Whispering, as she's known, brushing her hair.

MARIA (YouTube video): I also like the sounds of brushing.

CONOR DUFFY: It's designed to bring on a sensation known as ASMR, which believers describe as a mental massage or even a brain orgasm.

MARIA: ASMR stands for Autonomous Sensory Meridian Response. And it's usually described as a vibration or a tingling sensation that starts from the top of your head and travels down into your neck and your shoulders. Regular people feel calming sensation when somebody's brushing their hair. We feel like explosions in our head. It literally feels like a euphoria. So it just takes you to a much higher place than you would ever imagine.

(YouTube video): Hello. Today I wanted to show you another tutorial on how to fold towels in very decorative ways.

CONOR DUFFY: The triggers for ASMR can be, well, bizarre. Half a million people tuned in just to watch Maria fold towels.

MARIA (YouTube video): And I wanted to read to you a little article that has been posted in ...

CONOR DUFFY: 400,000 more tuned in to watch her reading the newspaper. All up, more than 80 million people have watched her videos.

Maria works from a home studio in Baltimore in the United States, recording the videos that have sparked a global craze. She's had stalkers and doesn't want to give her last name. There's no scientific evidence to support it, but Maria claims her whispering relieves anxiety and insomnia.

MARIA: You feel like you're a child and somebody's being very attentive to you, so it's very pleasant, especially in the hard time. People, literally, they pour their hearts out in the messages and just say that, "You changed my life."

CONOR DUFFY: In Ballarat in country Victoria, sisters Jemima, 16, and Lulu, 8, watch Maria's videos every day. It creates a sensation they describe as a brain tingle.

LULU BROOKS-WILCOX: It helps me sleep at night-time because I think a lot and, like, um, yeah, I think a lot and it clears my mind so I can just relax and sleep.

JEMIMA BROOKS: Mostly it makes me feel really relaxed and quite sleepy, but also it produces quite a nice feeling, kind of like you're having a gentle head scratch. It's quite nice.

LULU BROOKS-WILCOX: I did show mummy and she absolutely hated it. She just wanted to tell her to shush, yeah. She just wanted to throw my computer across the room.

VICTORIA BROOKS: Well I think it's very calming for both of them. I think that they both know that they've got a way of relaxing on tap, so that at any stage when they're feeling stressed or they need to sleep, they can just put on one of the videos and know that it'll have a beneficial effect for them.

DMITRI SMITH, ASMR ARTIST: G'day. How ya going? I thought what we would do is just give you a routine medical examination, just to check ...

CONOR DUFFY: Australia has its own ASMR sensation. He's Dmitri Smith from the Gold Coast. Today he's in character as Captain Aliathon exploring a foreign planet.

DMITRI SMITH: This planet is a class one habitable planet. Has a perfect atmosphere for human habitation.

A couple of my original ideas were to create, like, a futuristic doctor examination because people quite like medical examination. The most popular role play is probably what's referred to as the cranial nerve examination.

And now what I'll do is I'll just ask you to cover up your right eye and we'll do that one more time. Up and down.

CONOR DUFFY: While it's incredibly weird, it's also proving lucrative.

DMITRI SMITH: I'm hoping in the very near future that the money that I generate through YouTube's AdSense will be similar to what I might earn in a job so that I can focus on creating videos full-time.

CONOR DUFFY: In Melbourne, Lauren Ostrowski-Fenton, known as the Whispering Mother, is preparing her latest video. She believes ASMR works by triggering the release of the hormone oxytocin.

LAUREN OSTROWSKI-FENTON, ASMR ARTIST: There's no proven research at the moment, but a lot of people are saying and I believe that it takes you back to a memory you had with a care-giver. So it may be your mother or another care-giver. And when there's an experience between the mother and the child, the mother and the child both release oxytocin and this helps the child get to sleep and it helps the child to stop crying.

CONOR DUFFY: Lauren Ostrowski-Fenton also does one-on-one Skype sessions with clients, some of whom are war veterans with PTSD. Today she's performing ASMR on Paul from St Louis.

LAUREN OSTROWSKI-FENTON: And in your mind's eye, you imagine playing with these pebbles between your fingertips.

CONOR DUFFY: She and a growing online army have little time for the sceptics who dismiss it as a passing trend.

LAUREN OSTROWSKI-FENTON: What is a fad? A fad is something that suddenly explodes like mushrooms and then dies down. How can something that makes people feel just good be a fad? It is going to take over the world and it's going to be used by - like massage, as a supportive therapy.

LEIGH SALES: Conor Duffy reporting.