Orb hallucinations can actually be induced in multiple ways: e.g. via visual flicker or infrasound.
The study referenced,
Sensory dynamics of visual hallucinations in the normal population, Pearson, Chiou, Rogers et al.,
eLife October 2016 is interesting, but the hallucinations were generated in a specific experimental set-up.
Subjects watched a monitor displaying a broad white ring on a black background.
The ring was "turned on and off" (leaving a black screen in its absence) at various rates 5-30 Hz.
Subjects reported seeing grey blobs on the surface of the ring/ where the ring would have been, often travelling around the circumference.
From the author's Fig. 1:
Arguably the what the subjects saw could be described as "induced optical illusion" as well as "hallucination"; we don't normally describe e.g. optical afterimages as hallucinations (to be clear, the authors present evidence that the grey blobs cannot be solely explained as retinal afterimages and that cortical processing is involved).
There's no evidence that subjects saw orbs per se, or that their grey blobs moved from the fast-flickering, high-contrast ring area. Cool study though, thank you.
External Quote:
There is a story that an engineer, called Vick Tandy was working alone in a medical lab one evening in the 1980s. There were already reports that the lab was haunted. Vick reported suddenly feeling anxiety, cold and unease with a sense that he was being watched. He then noticed a grey object floating into in his peripheral vision.
Infrasound and the paranormal
The writer Naomi misspells "Vic Tandy",
External Quote:
Vic Tandy (1955 – 23 July 2005) was a British lecturer for information technology at
Coventry University, England, and an engineer. He was known best for his research into the relationship between
infrasound and
ghostly apparitions.
https://en.wikipedia.org/wiki/Vic_Tandy,
and he was working for a company designing medical ventilators (it seems, though that term isn't used), not in a medical lab.
And he didn't describe anything as "floating".
His experience doesn't seem to be connected to orbs as such. He (and a co-author) tells us what happened to him in
"The Ghost in the Machine", Vic Tandy and Tony R. Lawrence,
Journal of the Society for Psychical Research 62, 851 April 1998:
External Quote:
As he was writing he became aware that he was being watched, and a figure slowly emerged to his left. It was indistinct and on the periphery of his vision but it moved as V.T. would expect a person to. The apparition was grey and made no sound. The hair was standing up on V.T.'s neck and there was a distinct chill in the room. As V.T. recalls, "It would not be unreasonable to suggest I was terrified". V.T. was unable to see any detail and finally built up the courage to turn and face the thing. As he turned the apparition faded and disappeared.
http://www.richardwiseman.com/resources/ghost-in-machine.pdf, my emphasis added, PDF attached below.
Tandy ascribed his experience to an infrasound standing wave. He
might have underplayed the role of psychological factors such as suggestion for his specific unpleasant experience;
before it happened
External Quote:
...V.T. heard suggestions that the lab was haunted...
...but (perfectly sensibly) assumed this might be due to misperceptions of the various bits of medical ventilators "..wheezing away", lighting conditions, "...wild cats" (presumably feral cats), etc. etc.
His insight about infrasound occurred after the apparition incident.
I think it's accepted that in some circumstances infrasound can cause people to feel uneasy, "spooked".
The BBC 2 TV series
Uncanny, series 1 ep. 3 "The Oxford Exorcism" featured a fun (if low-powered!) experiment
(Available
on the BBC iPlayer here, apologies to non-UK people who probably can't get it, minutes 19:53-23:22 approx.)
A small group of student volunteers were told they were entering a haunted aircraft hangar at RAF Upper Heyford.
They were asked to place card "ghost" markers on the floor at any location where they felt particularly uneasy or had unpleasant sensations.
Unknown to them Steve Parsons, an engineer with expertise in infrasound had rigged up several emitters (19 Hz).
The theory was that the subjects would feel most uncomfortable where the infrasound was most intense.
The resulting distribution of markers suggests that infrasound might have played a role.