Does a -9 dB room cause hallucinations?

Question

Does being in an anechoic chamber cause hallucinations? According to several blogs (that likely copy each other), it does. The Orfield Laboratory in Minneapolis–Saint Paul, Minnesota, United States is reported to be the quietest room in the world with a rating of -9.4 dB sound pressure level (SPL). Several sources on the internet claim that this causes hallucinations and that nobody can stay there for long. It seems the blogs just copy each other. A selection:

From incredible-pictures.com:

Apparently it's so quiet, staying in there for a time will drive you insane. Nobody has been able to be in the room for more than forty five minutes.

From geekslop.com:

Even Mr. Oldfield, the owner of the sound chamber, admits that he can stay in the room for no more than 30 minutes. The sound of his heart valve drives him crazy.

Geekslop goes on to quote Mr. Oldfield, but do not provide any real citation.

From an article in TCB Magazine, Patricia Kelly, September 2008:

With no reverberation in the room, you have no spatial orientation cues. After about half an hour in the dark, you can become disoriented. Eventually, you might experience visual and aural hallucinations.

Huffington post:

The quiet chamber amplifies even the slightest noise, making people accurately aware of anything, including the sound of their heart beating. In fact, the sensation is so intense -- including the possibility of hallucinations -- that no one has been able to stay in the room longer than 45 minutes, according to the Deccan Chronicle.

This news has a link to the Deccan Chronicle which is now dead.

Is there any evidence for those claims? Does being in such a quiet room cause hallucinations, to such a degree that nobody is able to be there for long? 

Answer 1

The first reports of hallucinations during perceptual isolation were in 1953, by Heron, Bexton, and Hebb.^3,4

In 1960, Vosberg et al. found that an anechoic chamber produced a high incidence of auditory and visual hallucinations even within an hour.^1,2

Brady and Mason¹ aimed to "establish whether brief sensory deprivation in an anechoic chamber can elicit psychotic-like experiences, and perceptual distortions in particular, and whether these are related to hallucination proneness".

Their procedure was to have a subject spend "15 minutes in the chamber in complete darkness".

They concluded that "short-term sensory deprivation was found to lead to increases in several aspects of psychotic-like experience including perceptual disturbances, anhedonia, and paranoia. Hallucination prone participants experienced greater perceptual disturbances than nonprone participants".¹

A meta-study by Zuckerman and Cohen analyzed the experiments on perceptual isolation pre-1964.³ In my opinion, this was a very thorough review, examining "methods of confinement and restriction, conditions of illumination, duration of isolation, set, instructions and suggestions, reporting or verbalization instructions, sleep, subject populations, prior knowledge and expectations, intelligence and personality characteristics of subject's, stress response, and methods of obtaining reported visual and auditory sensations". Anechoic chambers and auditory restriction were not the focus of this study but were covered briefly.

Zuckerman and Cohen reviewed the wide range of reported visual sensations and argued that the term "hallucinations" should only be applied to visual sensations that are "meaningful" (people, objects, scenes) as opposed to idioretinal responses (light flashes, spots, shapes). Auditory hallucinations have been obtained in both darkness and diffuse light settings. Their review also showed several studies that reported the highest incidence of reported visual sensations during the first hour of isolation, with incidence dropping off after that.

(I'll add more to this answer later.)

References

^{1. OJ Mason, F Brady. The Psychotomimetic Effects of Short-Term Sensory Deprivation. The Journal of nervous and mental disease, 2009}

^{2. R. Vosberg, N. Fraser, J. Guehl. Imagery Sequence in Sensory Deprivation. AMA Arch Gen Psychiatry. 1960; 2(3):356-357}

^{3. M. Zuckerman, N. Cohen. Sources of Reports of Visual and Auditory Sensations in Perceptual Isolation Experiences.}

^{4. W. Heron, W.H. Bexton, and D.O. Hebb Cognitive effects of a decreased variation to the sensory environment.. Amer. Psychologist, 1953, 8, 366.}

Answer 2

Sensory Deprivation

Apparently if you block or disrupt any of the senses for long enough it can cause hallucinations. So the answer would be yes for some people hallucinations are a possibility.

Your question reminded me of floatation tanks, otherwise known as isolation chambers, where you float yourself in highly concentrated saltwater in a light and sound proof chamber. The very purpose of which is to deprive your senses in order to achieve a high meditative state. Some people use psychedelics in combination to enhance the hallucinatory effect.

Answer 3

There is a least one article written by someone who enjoyed their time in the Orfield anechoic chamber. He mentioned that the human body itself produces a substantial amount of noise (heart beating, lungs breathing, digestive tract rumbling), and the absolute quiet of the chamber highlights these sounds.

The Guardian - Experience the quietest place on earth

It is possible that the hallucinations people refer to are in fact routed in their unfamiliarity with the sounds of their own bodies.